Koestler, L., Koestler, A.G., Koestler, M.A., y Koestler, V.J.,
«Improving sustainability using incentives for operation and maintenance : the concept of water-person-years»,
Waterlines, an international journal of water, sanitation and waste, pp. p. 147-162 : 2 fig., 1 photogr., 2010.