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Evaluating the use of friend or family controls in epidemiologic case-control studies

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Evaluating the use of friend or family controls in epidemiologic case-control studies

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1

Evaluating the Use of Friend or Family Controls in Epidemiologic Case-Control Studies

by

Charlie Zhong

A Thesis Presented to the
FACULTY OF THE USC GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of
the Requirements for the Degree
MASTER OF SCIENCE
(APPLIED BIOSTATISTICS AND EPIDEMIOLOGY)

August 2016

2

Acknowledgement

I would like to acknowledge; my thesis committee, Drs. Myles Cockburn, Wendy Cozen and
Dennis Deapen for their support, Drs. Sophia Wang and Leslie Bernstein for their guidance, the
study participants for their continued cooperation in our research, Ms. Cynthia Quince and Teri
Terrusa, whose diligence made this study possible, and finally my parents for their unwavering
support.

The collection of cancer incidence data used in this study was supported by the California
Department of Public Health pursuant to California Health and Safety Code Section 103885;
Centers for Disease Control and Prevention’s (CDC) National Program of Cancer Registries,
under cooperative agreement 5NU58DP003862-04/DP003862; the National Cancer Institute’s
Surveillance, Epidemiology and End Results Program under contract HHSN261201000140C
awarded to the Cancer Prevention Institute of California, contract HHSN261201000035C
awarded to the University of Southern California, and contract HHSN261201000034C awarded
to the Public Health Institute. The ideas and opinions expressed herein are those of the author(s)
and endorsement by the State of California, Department of Public Health, the National Cancer
Institute, and the CDC or their Contractors and Subcontractors is not intended nor should be
inferred.

3

Table of Contents
Abstract ..........................................................................................................................................4

Introduction ...................................................................................................................................6
Case-control study recruitment ...................................................................................................6
Alternative control recruitment strategies ...................................................................................6
Purpose of this thesis ...................................................................................................................7

Methods ...........................................................................................................................................8
Parent case-control study ............................................................................................................8
Identification of alternate controls ..............................................................................................8
Abbreviated questionnaire administration ..................................................................................9
Analytic methods ..........................................................................................................................9

Results ..........................................................................................................................................11
Willingness of case patients to provide names of family and/or friends to serve as potential
controls ......................................................................................................................................11
Willingness of identified friend or family controls to participate in an epidemiology study and
complete a questionnaire ...........................................................................................................11
Comparability of the questionnaire responses from participating friend or family controls and
the original control ....................................................................................................................12

Tables ...........................................................................................................................................14
Table 1. Response Rates for NHL Case Patients, Highest Rank Matched Friend, and Highest
Rank Matched Family Member Willing to Participate in a Health Study .................................11
Table 2. Comparison of Highest Rank Matched Friend and Family Controls, to the Original
Study’s Matched Neighborhood Controls .................................................................................11

Discussion .....................................................................................................................................17

References ....................................................................................................................................19

4

Abstract

Background: Traditional methodologies for identifying and recruiting controls in epidemiologic
case-control studies, such as random digit dialing or neighborhood walk, suffer from declining
response rates. Here, we explore the feasibility and comparability of using alternative sources of
controls, specifically friend and family controls.

Methods: We leveraged data from a recently completed case-control study of non-Hodgkin
lymphoma (NHL) among women in Los Angeles County where controls from the parent study
were ascertained by neighborhood walk. The objective of this feasibility study was to recruit a
racially/ethnically diverse 10% sample of the original ~1000 female NHL cases. We calculated
participation rates among NHL case patients who were willing and able to provide information
on potential friend or family controls; we also calculated participation rates among identified
friend and family controls. Participating controls were given a brief version of the parent NHL
study questionnaire and their responses were compared to responses of matched controls from
the parent study.

Results: Of the 182 NHL case patients contacted, 111 (61%) agreed to participate in our
feasibility study. Among these women, 40 (36%) provided names and contact information for
potential family member and friend controls, 19 (17%) only provided names and contact
information for potential family controls, and 11 (10%) only provided names and contact
information for potential friend controls. We identified and recruited a friend control for 46
(92%) of the 51 identified by case patients and a family control for 54 (92%) of the 59 identified.
Compared to the original controls who were individually matched to case-patients in the case-

5

control study, family controls significantly differed by sex and household income. Overall
demographic and other characteristics were similar between friend controls and the original
study’s neighborhood controls.

Conclusion: The apparent comparability of neighborhood controls to friend and family controls
among respondents in this study suggests that these alternative methods of control identification
can serve as a complementary source of eligible controls in epidemiologic case-control studies.

6

Introduction

Case-control study recruitment.
A present challenge in conducting epidemiologic case-control studies is the identification
and recruitment of suitable controls in a cost-efficient manner. The response rates, and resulting
validity, of widely used approaches for recruitment of population-based controls, such as random
digit dialing (RDD) and neighborhood walk, have declined. Response rates for RDD have fallen
from 75-80% in the 1980s to 55-60% in the 2000s
1-5
, largely attributed to the use of caller
identification and increasing cellular phone usage
6
. Falling response rates increase the amount
of resources required to identify suitable controls, particularly for approaches like neighborhood
walk
7
and for some minority populations which require multiple follow-up attempts to ascertain
a successful recruit
8,9
.

Alternative control recruitment strategies.
Alternative strategies for identifying and recruiting controls have been proposed. Given
the rise in number of households who rely on cell phones as their primary or exclusive mode of
communication
10
, one alternative strategy is by modifying RDD to incorporate cell phone
numbers in place of or in conjunction with traditional landline RDD
11
. Initial research to
evaluate the feasibility of this method has already faced significant challenges. For instance,
area codes are not necessarily indicative of geographical location and the use of caller ID may
prevent case patients from answering calls from unknown numbers
11,12
. Long-debated
alternative methods for epidemiologic recruitment of controls include recruitment of case
patients’ friends and/or case patients’ family members
13-16
. These methods have not been
widely employed because of possible limitations, including: (i) overmatching controls by

7

exposures, as friend and family tend to engage in similar behaviors and live in similar areas
17-19

and (ii) potential bias among friend controls towards extroverts whereby introvert case patients
may be less inclined to nominate friends
18
. However, for some scientific questions, the use of
such controls could be suitable; specifically, the use of family controls is considered a strength
for studies aimed at identifying gene associations
20-23
.

Purpose of this thesis.
In this this, we assess the feasibility of identifying and recruiting family or friend controls
for epidemiologic case-control studies. Based on a racially/ethnically diverse 10% sample of
female non-Hodgkin lymphoma (NHL) patients in Los Angeles County, we evaluated: (i) the
willingness of case patients to provide names of family and/or friends as possible controls; (ii)
the willingness of identified friend or family controls to participate in an epidemiologic study
and complete a questionnaire; and (iii) the comparability of the questionnaire responses from
participating friend or family control to controls recruited by neighborhood walk.

8

Methods
Parent case-control study.
From 2004-2008, we conducted a case-control study of 1006 female B-cell non-Hodgkin
lymphomas and 1038 matched controls in Los Angeles County. Case patients were identified by
the Los Angeles County Cancer Surveillance Program (CSP) and controls were recruited by
neighborhood walk, matched to case patients within a 5 year age group, race, and socioeconomic
status. Specifically, recruiting control participants involved walking neighborhoods and
obtaining a census for all households within the series of addresses to be surveyed, until an
eligible matched control was identified. This methodology resulted in an 85% response rate
among controls, however certain race/ethnic groups (e.g., Asians) required additional time and
effort to recruit (per control) than others (e.g., Caucasians). All case patients were interviewed in
person and asked detailed questions about their health, including anthropometric characteristics
and lifestyle factors.

Identification of alternative controls.
We recontacted 182 living NHL case patients and asked if they were willing to
participate in a feasibility study aimed to explore alternative methods for conducting
epidemiologic studies. A case patient’s willingness to participate upon informed consent was
subsequently followed by a request for names and contact information of three friends and three
family members, preferably siblings or cousins who were similar in age (within 10 years), race,
and sex to the case patient. Case patients were asked to contact their respective controls first and
then to provide the potential controls’ name and contact information once the potential control
gave their permission for the case patient to do so. We attempted to recruit and interview each of

9

the family members and friends for whom we obtained contact information. In order to not
disclose the case patient’s diagnosis, potential controls were asked if they were willing to
participate in a “health study”. Upon a potential control’s consent to participate, an abbreviated
version of parent study questionnaire was administered during a telephone interview.

Abbreviated questionnaire administration.
Among consented controls, the abbreviated questionnaire included targeted areas of
interest delineated in Table 2: (i) demographics, including highest education level attained,
annual household income, and marital status; (ii) lifestyle and behavioral characteristics,
including history of smoking and alcohol, height and weight, physical activity, and aspirin use;
and (among female respondents) (iii) reproductive characteristics, including use of birth control
or menopausal hormones, number of full-term pregnancies, menstrual and hysterectomy status,
and history of breastfeeding; and (iv) health behavior, including frequency of mammograms and
Pap smears.

Analytic methods.
First, we calculated the response rates among contacted case patients representing their
willingness to provide names and contact information for potential friend or family controls
defined as the total number of case patients who agreed to participate divided by the total number
of case patients contacted. Second, among case patients who consented to participate, we
calculated the response rate for providing the requested information (e.g., names and valid
telephone number) on respective friend or family controls. This response rate was defined as the
total number of case patients who agreed to participate and provided the requested information

10

divided by the total number of case patients who consented to participate in this feasibility study.
Third, among identified friends and family members with contact information whom we
attempted to recruit, we calculated the respective response rates of controls that were willing to
participate in our study. This response rate was defined as the number of contacted controls who
agreed to participate and completed our questionnaire divided by the total number of controls
contacted. These response rates were calculated overall, by race/ethnicity, and sex (Table 1).
Finally, we compared demographic information and questionnaire responses of highest
ranked family control and friend control (to approximate a 1:1 matching method) to the
responses from the matched neighborhood matched control who was recruited in the parent case-
control study for the case patient. The following criteria were used to rank the family and friend
controls: (1) same sex and older than case patient; (2) opposite sex and older; (3) same sex and
younger; (4) opposite sex and younger. We compared the frequencies (percent) of the
questionnaire responses by calculating the Fisher’s exact test for statistical significance using
SAS 9.3 (SAS Institute, Cary, NC). These results are shown in Table 2.

11

Results
Willingness of case patients to provide names of family and/or friends to serve as potential
controls.
Of the 182 living NHL case patients contacted, 111 (61%) agreed to participate in our
feasibility study (Table 1). Of the 111, 40 (36%) were able to provide names and contact
information for potential family member and friend controls, 19 (17%) were only able to provide
names and contact information for potential family controls, and 11 (10%) were only able to
provide names and contact information for potential friend controls. There were 41 (37%) case
patients who consented to participate but were unable to provide names/contact information for
friends or family, citing that the potential controls they contacted were unwilling to participate.
The 71 (39%) case patients who did not consent to participate cited varying reasons, including:
(i) not having told any of their friends or family that they were diagnosed with NHL (n=4); (ii)
being willing to participate but not having any friend or family of the same race or general age
(n=14); the remaining 37 were soft refusals whereby the case patient verbally agreed to
participate but was ultimately unable to be reached. Participation rates were relatively consistent
by race/ethnicity. Of participating case patients, the ability to provide contact information for
potential friend controls was highest among Asians (60%) and non-Hispanic Whites (60%), and
lowest among Blacks (26%) and Hispanics (29%). The ability to provide contact information for
potential family controls was highest among Hispanic (62%) and non-Hispanic Whites (60%)
and lowest among Blacks (34%).

12

Willingness of identified friend or family controls to participate in an epidemiologic study
and complete a questionnaire.
In all, we attempted to contact 102 potential friend controls who were identified by 51
NHL case patients. We were able to contact 96 friend controls (for 50 case patients); for one
case patient, we were unable to contact any of the potential friend controls listed. Of the 96
potential friend controls contacted, 83 controls (from 46 case patients) provided consent and
completed the questionnaire. Of the 46 highest ranked friend controls (matched 1:1 to each case
patient); 33 were of the same sex and older, 1 was of the opposite sex and older, 11 were of the
same sex and younger, and 1 was of the opposite sex and younger (Table 1). These distributions
did not appear to vary across racial/ethnic groups.
Of 99 potential family controls (representing 59 case patients), we successfully contacted
92 potential family controls (representing all 59 case patients), of which 78 consented and
completed a questionnaire. These 78 family controls were from 54 case patients, leaving 5 case
patients without an identified family control. Of the 54 highest ranked controls, 17 were older
siblings or cousins of the same sex, 5 were older siblings or cousins of the opposite sex, 26 were
younger siblings or cousins of the same sex, and 6 were younger siblings or cousins of the
opposite sex (Table 1).

Comparability of the questionnaire responses from participating friend or family control
and the original control.
Among demographic characteristics, statistically significant (P<0.05) differences were
observed between family controls and the original controls with respect to sex; the 20% of
family controls who were male reflected the difficulty in ascertaining family controls of the same

13

sex for all case patients (Table 2). Annual household income was also lower among the family
controls. Although not statistically significant, family controls were generally younger than the
original neighborhood controls. Overall, friend controls appeared similar to the original study’s
neighborhood controls.

14

Tables

Table 1. Response Rates for NHL Case Patients, Highest Rank Matched Friend, and Highest Rank Matched Family Member Willing to Participate
in a Health Study.

Total

Asians

Blacks

Whites

Non-Hispanic
White

Hispanic
White
Case Patients
Alive and contacted 182

46

45

91

56

35
Agreed to Participate 111 61%

30 65%

27 60%

54 59%

33 59%

21 60%

Nominated both friends and family members 40 36%

15 50%

5 19%

20 37%

16 48%

4 19%

Nominated only friends 11 10%

3 10%

2 7%

6 11%

4 12%

2 10%

Nominated only family members 19 17%

2 7%

4 15%

13 24%

4 12%

9 43%

Agreed to participate but reported no willing friend or family 41 37%

10 33%

16 59%

15 28%

9 27%

6 29%
Refused (includes nonrespondents after initial contact) 71 39%

16 35%

18 40%

37 41%

23 41%

14 40%

Highest Rank Friend Controls (1 control per case patient)
Attempted to contact 51

18

7

26

20

6
Able to contact 50 98%

18 100%

7 100%

25 96%

19 95%

6 100%

Completed Questionnaire 46 92%

15 83%

7 100%

24 96%

19 100%

5 83%

Older, same sex 33 72%

13 87%

5 71%

15 63%

13 68%

2 40%

Older, different sex 1 2%

0 0%

0 0%

1 4%

1 5%

0 0%

Younger, same sex 11 24%

2 13%

2 29%

7 29%

5 26%

2 40%

Younger, different sex 1 2%

0 0%

0 0%

1 4%

0 0%

1 20%

Refused 4 8%

3 17%

0 0%

1 4%

0 0%

1 17%
Unable to Contact 1 2%

0 0%

0 0%

1 4%

1 5%

0 0%

Highest Rank Family Members (1 control per case patient)
Attempted to contact 59

17

9

33

20

13
Able to contact 59 100%

17 100%

9 100%

33 100%

20 100%

13 100%

Completed Questionnaire 54 92%

16 94%

9 100%

29 88%

20 100%

9 69%

Older, same sex sibling 16 30%

2 13%

3 33%

11 38%

5 25%

6 67%

Older, same sex cousin 1 2%

0 0%

0 0%

1 3%

1 5%

0 0%

Older, opposite sex sibling 4 7%

2 13%

0 0%

2 7%

2 10%

0 0%

Older, opposite sex cousin 1 2%

0 0%

0 0%

1 3%

0 0%

1 11%

Younger, same sex sibling 22 41%

8 50%

4 44%

10 34%

7 35%

3 33%

Younger, same sex cousin 5 9%

3 19%

1 11%

1 3%

1 5%

0 0%

Younger, opposite sex sibling 5 9%

1 6%

1 11%

3 10%

3 15%

0 0%

Younger, opposite sex cousin 1 2%

0 0%

0 0%

1 3%

1 5%

0 0%

Refused 4 7%

1 6%

0 0%

3 9%

0 0%

3 23%
Unable to Contact 0 0% 0 0% 0 0% 0 0% 0 0% 0 0%

15

Table 2. Comparison of Highest Rank Matched Friend and Family Controls, to the Original Study’s Matched Neighborhood Controls

Friend Control Comparison (n=46)

Family Control Comparison (n=54)

Original Study:
Matched Controls

Highest Ranked
Friend Control

Original Study:
Matched Controls

Highest Ranked
Family Control
Characteristics

N percent

N percent p-value

N percent

N percent p-value
Demographics
Sex

Male

0 0%

2 4%

0 0%

11 20%

Female

46 100%

43 96% 0.2418

54 100%

43 80% 0.0006

Race/Ethnicity

Non-Hispanic White 19 41%

19 41%

19 41%

19 41%

Hispanic White 5 11%

5 11%

5 11%

5 11%

Black 7 15%

7 15%

7 15%

7 15%

Asian 15 33%

15 33% 1.0000

15 33%

15 33% 1.0000

Reference Age (median/range, years) 58 24-78

59 25-83

58.5 24-78

55 20-83

<35 3 7%

4 9%

4 7%

5 9%

35-44 5 11%

3 7%

5 9%

4 7%

45-54 7 15%

8 18%

13 24%

16 30%

55-64 18 39%

15 33%

18 33%

15 28%

65-74 8 17%

8 18%

9 17%

10 19%

>75 5 11%

7 16% 0.9434

5 9%

4 7% 0.9692

Education
Less than High School 2 4% 1 2% 3 6% 4 7%
High School Graduate 6 13% 5 11% 6 11% 8 15%
Some College 10 22% 15 33% 12 22% 14 26%
College Graduate 28 61% 24 53% 0.6259 33 61% 28 52% 0.8227
Annual household income

<$25,000 3 8% 6 14% 3 6% 11 22%
$25,000-$50,000 9 24% 12 28% 10 21% 15 30%
$50,000-$90,000 8 21% 5 12% 12 26% 11 22%
>$90,000 18 47% 20 47% 0.6267 22 47% 13 26% 0.0497
Ever Married

Yes 43 93% 43 96% 51 94% 48 89%
No 3 7% 2 4% 1.0000 3 6% 6 11% 0.4886

Lifestyle characteristics
Smoking

Ever 20 43%

21 47%

23 43%

17 31%

Never 26 57%

24 53% 0.8344

31 57%

37 69% 0.3191

Alcohol

Ever 21 46%

23 51%

21 39%

31 57%

Never 25 54%

22 49% 0.6768

33 61%

23 43% 0.0826

16

BMI at 20 years old (kg/m2)

<18.5 7 15%

14 31%

6 11%

7 13%

18.5-25 36 78%

28 62%

43 80%

39 72%

>25 3 7%

3 7% 0.1824

5 9%

8 15% 0.6538

Adult BMI (kg/m2)

<18.5 2 4%

2 4%

1 2%

1 2%

18.5-25 26 57%

27 60%

26 48%

30 56%

>25 18 39%

16 36% 0.9336

27 50%

23 43% 0.7778

Reproductive characteristics
Birth Control Pill

Ever 29 66%

29 67%

30 70%

26 60%

Never 15 34%

14 33% 1.0000

13 30%

17 40% 0.4977

Pregnancies

Never pregnant 9 21%

9 22%

7 18%

10 24%

One child 7 16%

8 20%

4 10%

8 19%

> 1 child 27 63%

24 59% 0.9527

29 73%

24 57% 0.3219

Menstrual Status

Currently menstruating 12 27%

13 30%

12 28%

20 47%

Natural menopause 18 41%

18 42%

20 47%

12 28%

Induced menopause 14 32%

12 28% 0.9272

11 26%

11 26% 0.1385

Menopausal Hormone Use (any)

Yes 29 66%

22 51%

26 60%

16 37%

No 15 34%

21 49% 0.1948

17 40%

27 63% 0.0516

Hysterectomy

Yes 12 38%

13 39%

8 26%

10 36%

No 20 63%

20 61% 1.0000

23 74%

18 64% 0.5721
Health behavior

Mammogram (ever)

Yes 36 82%

37 86%

36 84%

35 81%

No 8 18%

6 14% 0.7717

7 16%

8 19% 1.0000

Mammogram Frequency

Annually 21 58%

27 73%

23 64%

22 63%

Less than annually 15 42%

10 27% 0.2231

13 36%

13 37% 1.0000

Pap Smear Frequency

Annually 23 53%

26 60%

24 57%

25 61%

Less than annually 20 47%

17 40% 0.6634

18 43%

16 39% 0.8243

17

Discussion
Results from our feasibility study testing recruitment of different types of controls in a
racially/ethnically diverse case-control study of NHL suggest that recruitment of friends and
family members as a primary source of controls present a significant challenge for epidemiologic
studies. Nevertheless, the high response rate among identified controls makes utilization of
friend or family controls a viable method for supplementing other methodologies of control
ascertainment. Friend controls in general had a higher response rate than family controls and
their responses were closely aligned those of our original neighborhood controls.
Case patient response rates were similar across racial/ethnic groups; however the ability
to provide family or friend controls differed. 40% of the NHL case patients identified as Black
were able to provide information of a friend or family member who could serve as a potential
control. This contrasts with two-thirds of Asian and 75% of non-Hispanic White NHL case
patients who were able to do so, which is consistent with other studies
15,24
. We required the
participating case patients to contact their potential controls before we made an attempts to do so,
likely resulting in our higher response rate among the controls (92%) compared to previously
reported efforts (48-70%)
13,19,24,25
. We cannot exclude the possibility of differential
participation rates in the general population when men are included
13,15
as our parent study was
restricted to female NHL case patients. Because the median age of diagnosis for NHL is 66
years, our ability to identify older family controls was likely diminished
26
. It is possible that
higher participation rates might be achieved for disease endpoints with a lower median age of
diagnosis.
Prior studies that have used friend or family controls have been conducted primarily
within non-Hispanic White populations and have reported that 60-100% of case patients

18

provided controls
13,15,21,24,27-29
. Our response rates for non-Hispanic Whites were comparable to
these previous efforts. Although the success of this methodology appeared to be equivalent
among Asian-Americans, response rates in our study among Black and Hispanic populations
remained low.
A number of reasons account for the relatively large percentage of case patients who
refused or were unable to provide potential controls. Some case patients refused to participate
because they had not discussed their NHL diagnoses with friends or family members. The
severity of the cancer diagnosis may also impact the willingness to discuss it with others
14
. It is
thus possible that those who had more severe disease and have since died would have been less
likely to have participated
30
. Several case patients also noted they were unable to provide
family members who resided in the United States, which is a particularly important issue to
consider when applying this methodology to immigrant populations.
In summary, ascertaining potential friend and family control information from case
patients at the time of case recruitment could supplement other methodologies for control
identification and recruitment in epidemiologic studies. Continued efforts to identify and
improve alternative methods
31,32
for control recruitment in population-based case-control studies
are needed.

19

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Abstract (if available)

Abstract Background: Traditional methodologies for identifying and recruiting controls in epidemiologic case-control studies, such as random digit dialing or neighborhood walk, suffer from declining response rates. Here, we explore the feasibility and comparability of using alternative sources of controls, specifically friend and family controls. ❧ Methods: We leveraged data from a recently completed case-control study of non-Hodgkin lymphoma (NHL) among women in Los Angeles County where controls from the parent study were ascertained by neighborhood walk. The objective of this feasibility study was to recruit a racially/ethnically diverse 10% sample of the original ~1000 female NHL cases. We calculated participation rates among NHL case patients who were willing and able to provide information on potential friend or family controls

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Asset Metadata

Creator Zhong, Charlie Chengyi (author)

Core Title Evaluating the use of friend or family controls in epidemiologic case-control studies

School Keck School of Medicine

Degree Master of Science

Degree Program Applied Biostatistics and Epidemiology

Publication Date 06/29/2016

Defense Date 06/29/2016

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag case-control methods,OAI-PMH Harvest

Format application/pdf (imt)

Language English

Contributor Electronically uploaded by the author (provenance)

Advisor Cockburn, Myles (committee chair), Cozen, Wendy (committee member), Deapen, Dennis (committee member)

Creator Email charliez@usc.edu

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c40-258596

Unique identifier UC11279442

Identifier etd-ZhongCharl-4480.pdf (filename),usctheses-c40-258596 (legacy record id)

Legacy Identifier etd-ZhongCharl-4480.pdf

Dmrecord 258596

Document Type Thesis

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Rights Zhong, Charlie Chengyi

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Access Conditions The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the a...

Repository Name University of Southern California Digital Library

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