1. Geochemistry, Groundwater and Pollution;Appelo,1993
2. Thirty-five years of continuous discharge of secondary treated effluent onto sand beds;Aulenbach;Ground Water,1975
3. Baxter, K.M., Clark, L., 1984. Effluent recharge. The effects of effluent recharge on grondwater quality. Technical Report 199, Water Research Centre, United Kingdom.
4. Septic Tank System Effects on Groundwater Quality;Canter,1985
5. Charalambous, A.N., 1982. Problems of groundwater development in the Sana'a Basin. Yemen Arab Republic, Proceedings of the Symposium ‘Improvements of Methods of Long Term Prediction of Variations in Groundwater Resources and Regimes Due to Human Activity’, IAHS Publication no. 136.