1. On-site sanitation. when the pits are full—Planning for resource protection in faecal sludge management;Strauss;Ver. Wasser Boden Lufthyg,2000
2. The State of African Cities 2008,2008
3. The global situation;Strande,2014
4. Progress on Drinking Water and Sanitation—2014 Update
http://www.unicef.org/media/files/JMP_2014_Update.pdf