1. Ministry of Land, Infrastructure, Transport and Tourism of Japan, Water resources in Japanhttp://www.mlit.go.jp/tochimizushigen/mizsei/water_resources/contents/current_state2.html
2. The Atlas of Water;Black,2009
3. Prediction of CO2 emissions associated with residential plumbing equipment;Yasutoshi;J. Soc. Heat. Air-Cond. Sanit. Eng. Jpn.,2010
4. Creation of Carbon Credits by Water Saving
5. CO2 Emission Factor for Rainwater and Reclaimed Water Used in Buildings in Japan