1. Census of Population and Housing. Department of Census and Statistics, Sri Lanka. Available at http://www.statistics.gov.lk/page.asp?page=Population%20and%20Housing Accessed July 16, 2019.
2. Country HIV Factsheets, UNAIDS. Available at https://www.unaids.org/en/regionscountries/countries/srilanka Accessed on July 22, 2019.
3. Annual Report 2018. Colombo: National STD/AIDS Programme, Ministry of Health, Sri Lanka; 2018.
4. Abdul-Quader AS, Baughman AL, Hladik W. Estimating the size of key populations: current status and future possibilities. Curr Opin HIV AIDS. 2014; 9(2):107–14. doi: 10.1097/COH.0000000000000041 24393694
5. Quaye S, Fisher Raymond H, Atuahene K, Amenyah R, Aberle-Grasse J, McFarland W, et al. Critique and Lessons Learned from using Multiple Methods to Estimate Population Size of Men who have Sex with Men in Ghana. AIDS Behav. 2015; 19 Suppl 1:16–23.
6. UNAIDS/WHO Working Group on Global HIV/AIDS and STI Surveillance. Guidelines on Estimating the Size of Populations Most at Risk to HIV. Geneva: World Health Organization; 2010.
7. Wesson P, Reingold A, McFarland W. Theoretical and Empirical Comparisons of Methods to Estimate the Size of Hard-to-Reach Populations: A Systematic Review. AIDS Beh. 2017;21(7):2188–2206.
8. National Size Estimation of Most at Risk Populations (MARPs) for HIV in Sri Lanka. Colombo: National STD/AIDS Control Programme; 2013.
9. Yu D, Calleja JM, Zhao J, Reddy A, Seguy N. Estimating the size of key populations at higher risk of HIV infection: a summary of experiences and lessons presented during a technical meeting on size estimation among key populations in Asian countries. Western Pac Surveill Response J. 2014;5(3):43–9. doi: 10.5365/WPSAR.2014.5.2.008 25320676
10. Thein ST, Aung T, McFarland W. Estimation of the number of female sex workers in Yangon and Mandalay, Myanmar. AIDS Behav. 2015; 19(10):1941–7. doi: 10.1007/s10461-015-1169-9 26267254
11. Johnston LG, Prybylski D, Raymond HF, Mirzazadeh A, Manopaiboon C, McFarland W. Incorporating the service multiplier method into respondent-driven sampling surveys to estimate the size of hidden and hard-to-reach populations. Case studies from around the world. Sex Transm Dis 2013; 40: 304–301. doi: 10.1097/OLQ.0b013e31827fd650 23486495
12. Emmanuel F, Isac S, Blanchard JF. Using geographical mapping of key vulnerable populations to control the spread of HIV epidemics. Expert Rev Anti Infect Ther. 2013;11(5):451–3. doi: 10.1586/eri.13.33 23627850
13. Thilakavathi T, Chakrapani V, Selvaraj V, Noronha E, Narang A, Mehendale S. Mapping and Size Estimation of Hijras and Other Trans-Women in 17 States of India: First Level Findings. Int J Health Sci Res. 2015; 5(10): 1–10.
14. Baral SD, Poteat T, Strömdahl S, Wirtz AL, Guadamuz TE, Beyrer C. Worldwide burden of HIV in transgender women: a systematic review and meta-analysis. Lancet Infect Dis. 2013;13(3):214–22. doi: 10.1016/S1473-3099(12)70315-8 23260128
15. Chakrapani V, Willie TC, Shunmugam M, Kershaw TS. Syndemic Classes, Stigma, and Sexual Risk Among Transgender Women in India. AIDS Behav. 2019;23(6):1518–1529. doi: 10.1007/s10461-018-2373-1 30565093
16. Report on the National Size Estimation of the Most at Risk Populations for HIV in Sri Lanka. Colombo: National STD/AIDS Control Programme; 2018.
17. Random Integer Set Generator. Available at https://www.random.org/integer-sets/ Accessed on 26 July 2019.
18. Integrated Biological and Behavioural Surveillance Survey among Key Populations at Higher Risk of HIV in Sri Lanka 2017/2018. Colombo: National STD/AIDS Control Programme and Management Frontiers, Ltd.; 2018.
19. Heckathorn DD. Respondent-driven sampling: A new approach to the study of hidden populations. Social Problems. 1997; 44(2): 174–199.
20. Handcock MS, Fellows IE, Gile KJ, 2014. RDS Analyst: Software for the Analysis of Respondent-Driven Sampling Data. Version 0.51.
21. Gile KJ. Improved Inference for Respondent-Driven Sampling Data with Application to HIV Prevalence Estimation. J Am Stat Assoc. 2011; 106: 135–146.
22. Khalid FJ, Hamad FM, Othman AA, Khatib AM, Mohamed S, Akh A, et al. Estimating the number of people who inject drugs, female sex workers, and men who have sex with men, Unguja Island, Zanzibar: results and synthesis of multiple methods. AIDS Behav. 2014;18(Suppl 1):S25–31.
23. Dalkey NC. The Delphi method: an experimental study of group opinion, RM-5888-PR. Santa Monica, CA: The RAND Corporation; 1969.
24. Quick Start Guide for Spectrum. Geneva: UNAIDS, 2018.
25. 2015 Size Estimation of Key Affected Populations in the Philippines. Manila: Epidemiology Bureau, Department of Health, Philippines, 2016.
26. Poudel T, Gupta S, Bhattarai Rajan, Rawal BB. Mapping and Size Estimation of Key Populations in Nepal. Journal of Gandaki Medical College-Nepal. 2019; 1 (12): 39–42.
27. Poteat T, Scheim A, Xavier J, Reisner S, Baral S. Global Epidemiology of HIV Infection and Related Syndemics Affecting Transgender People. J Acquir Immune Defic Syndr. 2016.15;72 Suppl 3:S210–9.
28. Size estimation of transgender population in Cambodia. Phnom Penh: Family Health International 360 Cambodia; 2013.
29. Quaye S, Fisher Raymond H, Atuahene K, Amenyah R, Aberle-Grasse J, McFarland W, et al. Critique and lessons learned from using multiple methods to estimate population size of men who have sex with men in Ghana. AIDS Behav. 2015;19 (Suppl 1):16–23.