title: [Study of family planning. I. Introduction].
mesh_terms: D002677:Chile; D003710:Demography; D005193:Family Planning Services; D049673:History, 20th Century; D007391:International Cooperation; D008800:Mexico; D012189:Retrospective Studies; D014944:World Health Organization
vernacular_title: El estudio de la planificación familiar. I. Introducción.