Ullrich, G.J.

Gohl, E., Ullrich, G.J. & Krappitz, U., 1991. Participatory approaches for cooperative group events : basic concepts, case study, practical tips 2nd rev. ed.ᵉ éd., Bonn, Germany: German Foundation for International Development (DSE). Available at: https://fr.ircwash.org/sites/default/files/152-13533.pdf.