Unknown,Unexplored,and Unseen Populations: An Introduction into the Truly Hidden Worlds of Drug and Alcohol Research

Lambert E. Y. Wiebel W. W. 1990 The collection and interpretation of data from hidden populations. Washington D.C.: National Institute on Drug Abuse Monograph 98.

Wiebel W.W. 1990 Identifying and gaining access to hidden populations. In The collection and interpretation of data from hidden populations, eds. Lambert E.Y. Wiebel W.W. , Washington D.C.: National Institute on Drug Abuse Monograph 98.