Biblio

B. A. Ryan and Mara, D. D., “Pit latrine ventilation : field investigation methodology”, vol. no. 4. World Bank, Washington, DC, USA, p. i, 16 p., 1983.

B. A. Ryan and Mara, D. D., “Ventilated improved pit latrines : vent pipe design guidelines”. World Bank, Washington, DC, USA, 1983.