* Peña Varón, M. and Mara, D. D. (2004). [https://sswm.info/sites/default/files/reference_attachments/VARON%202004%20%20Waste%20Stabilistion%20Ponds.pdf Waste Stabilisation Ponds]. Thematic Overview Paper. IRC International Water and Sanitation Centre, Delft, NL.