The Lack of Selection Bias in a Snowball Sampled Case-Control Study on Drug Abuse

Abstract
Lopes C S (Instituto de Medicina Social, State University of Rio de Janeiro, R. Sao Francisco Xavier 524, 7 andar, 20559-900 Rio de Janeiro-RJ, Brazil), Rodrigues L C and Sichieri R. The lack of selection bias in a snowball sampled case-control study on drug abuse. International Journal of Epidemiology 1996; 25: 1267–1270.