VAN DIJK, J.C. and OOMEN, J.H.C
(1978):
Slow Sand Filtration for Community Water Supply in Developing Countries. A Design and Construction Manual.
The Hague (The Netherlands):
World Health Organisation (WHO) International Reference Centre for Community Water Supply. Technical Paper, 11, pp.1-175.
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[Accessed: 07.08.2018]
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