L. F. Requena and de Quintanilla, E.,
“El Salvador : program for monitoring surface and groundwater in the watershed between the Barra de Santiago and El Impossible”, vol. no. 425. Water and Sanitation for Health Project (WASH), Arlington, VA, USA, p. xiii, 50 p. + 9 appendices: 2 map, 3 tab., 20 photogr., 1993.
