N. L. Calorama - Elburg,
«Hand drilled wells», vol. no. 3. Calorama Rural Development Service, Elburg, The Netherlands, p. 65 p. : fig., photogr., tab., tech. drwngs., 1997.
S. H. S. y Tene, C.,
«Letrina MFC - OPS/OMS». Pan American Health Organization (PAHO), Tegucigalpa, Honduras, p. 4 p. : 2 photogr., 2 tab., 1997.
P. Calvert,
«Seeing (but not smelling) is believing : Kerala's compost toilet»,
Waterlines, an international journal of water, sanitation and waste, pp. p. 30-32 : 2 drwngs., 2 photogr., 2 tab., 1997.