V. N. U. N. I. C. E. F. - Ha Noi y VN, V. Nam. Minis,
«Ve sinh gia dinh». Viet Nam, Ministry of Health, Hanoi, Viet Nam, p. 24 p., 1993.
J. P. Chudy, Arniella, E., y Gil, E.,
«Water quality assessment in Ecuador», vol. no. 390. Water and Sanitation for Health Project (WASH), Arlington, VA, USA, p. xiv, 71 p.: 11 fig., 1 map, 2 tab., 1993.