1. UNICEF (n.d.) Water Scarcity, Addressing the Growing Lack of Available Water to Meet Children’s Needs. https://www.unicef.org/wash/water-scarcity
2. Klobucista, C. and Robinson, K. (2022) Water Stress: A Global Problem That’s Getting Worse. https://www.cfr.org/backgrounder/water-stress-global-problem-thats-getting-worse
3. Khalaphallah, R. (2012) Greywater Treatment for Reuse by Slow Sand Filtration: Study of Pathogenic Microorganisms and Phage Survival. https://theses.hal.science/tel-00735857/document
4. The efficiency of the sand filtration unit mixed with different packing materials in drain water treatment in Egypt