D. T. Lauria, Wright, A. M., Hughes, J., Choe, K., Whittington, D., en Swarna, V.,
“Household demand for improved sanitation services : a case study of Kumasi, Ghana”, vol. no. 3. World Bank, Water and Sanitation Division, Washington, DC, USA, p. ix, 118 p.: 17 fig., 24 tab., 1992.
D. Whittington, Lauria, D. T., Wright, A. M., Choe, K., Hughes, J., en Swarna, V.,
“Households' willingness to pay for improved sanitation in Kumasi, Ghana: results of a contingent valuation study”, vol. SW 7. World Bank, Water and Sanitation Division, Washington, DC, USA, p. 4 p.: 1fig., 1 tab., 1992.
