@article{Heckathorn2002,
author = {Heckathorn, D.D.},
title= {Respondent-driven sampling II: Deriving valid population estimates from chain-referral samples of hidden populations},
year = {2002},
doi = {1525/sp.2002.49.1.11},
journal = {Social Problems },
volume = {49},
number = {1},
pages = {11--34},
}