1. Bieleman B., Diaz A., Merlo G., Kaplan CH. D. Lines across Europe: Nature and Extent of Cocaine Use in Barcelona, Rotterdam and Turin. Swets & Zeitlinger—Academic Publishing Division, Amsterdam 1993; 1–219
2. Snowball Sampling: Problems and Techniques of Chain Referral Sampling
3. Carlini-Cotrim B., Silva-Filho A. R., Barbosa M. T. S., Carlini E. A. Consumo de drogas psicotrÓpicas no Brasil em 1987 [Consumption of Psychotropic Drugs in Brazil during 1987]. Centre de Documentaão do Ministério da Saúde, Brasília 1989; 1–84