Helvetas -Moratuwa, LK

Moratuwa, L.K.Helvetas - & Moratuwa, L.K.Sarvodaya, 1991. Introduction to surveying, Nugegoda, Sri Lanka: Helvetas, Swiss Association for Development and Cooperation. Available at: https://fr.ircwash.org/sites/default/files/201-91IN-8893.pdf.