Use of lay opinion leaders to promote diffusion of health innovations in a community programme : lessons learned from the North Karelia project / P. Puska . [et al.] - Puska, Pekka; Koskela, Kaj; McAlister, A; Mäyränen, H; Smolander, A; Moisio, S; Viri, L; Korpelainen, V; Rogers, E. M (1986)