M. Wegelin en Dorcoo, K., “Water treatment in northern Ghana”, in Water, sanitation, environment and development : proceedings of the 19th WEDC conference, Accra, Ghana, 6-10 September 1993, 1993, pp. P. 111-114 : 2 fig., 1 tab.
1992
K. R. Bulusu en Nawlakhe, W. G., “Defluoridation”. National Environmental Engineering Research Institute, NEERI, Nagpur, India, p. viii, 61 p., [7] p. pl.: 8 fig., 18 tab., 1992.