Changes

* Robert Vuik, Don de Koning and Arjen van der Wal. [http://www.practica.org/wp-content/uploads/services/publications/drilling%20manuals/EN/Percussion%20manual%20drilling%20PRACTICA%20EN.pdf Percussion: Manual Drilling Series. Technical Training Handbook on Affordable Manual Well Drilling]. Practica Foundation, June 2010. French version: [http://www.practica.org/wp-content/uploads/services/publications/drilling%20manuals/FR/Percussion%20manual%20drilling%20PRACTICA%20FR.pdf FORAGE À LA PERCUSSION: Série forage manuel].

* [http://www.wellspringafrica.org/manual.asp Drilling Wells by Hand], Cliff Missen, Wellspring Africa, draft 4 - Manual on Percussion drilling, well construction, manufacturing tools. [http://www.wellspringafrica.org/drildesc.htm Website of WellspringAfrica]