Johnson, B.

Webster, M. & Johnson, B., 1990. Africare Nigeria: field investigation of causes of failed water supply boreholes and pumping systems in Imo and Akwa Ibom States, Nigeria, (Wash field report no. 286) Arlington, VA, USA: Water and Sanitation for Health Project (WASH). Available at: https://nl.ircwash.org/sites/default/files/824-NG90-6911.pdf.