D. Whittington, D. T. Lauria and X. Mu, “Paying for Ur- ban Water Services: A Study of Water Vending and Will- ingness to Pay for Water in Onitsha, Nigeria,” World Bank Publications, Washington DC, 1989.
 B. Baisa, L. Davis, S. W. Salant and W. Wilcox, “The Welfare Costs of Unreliable Water Service,” Unpublished MPRA Paper, 2008. http://www.mpra.ub.uni-muenchen.de/9812
 H. T. Ishaku, A. A. Peters, A. Haruna and F. M. Dama, “The Role of Private Water Vending in Nigerian Peri- Urban Informal Settlements: Implications for Policy Mak- ers,” Journal of Water Resource and Protection, Vol. 2, No. 12, 2010, pp. 1082-1087. doi:10.4236/jwarp.2010.212127
 J. C. Headley, “The Relation of Family Income and Use of Water for Residential and Commercial Purpose in the San Francisco—Oakland Metropolitan Area,” Land Economics, Vol. 39, No. 4, 1963, pp. 441-449. doi:10.2307/3144849
 M. Kjellen, “Water Vending in Dares Salaam, Tanzania,” In: B. Calas and C. A. Mumma Martinon, Eds., Shared Waters, Shared Opportunities: Hydropolitics in East Africa, Nairobi and Mkukina Nyota Publishers Ltd., Tanzania, 2010, pp. 173-184.