“The Sacred Heart Review, Volume 4, Number 19 - ngày 4 tháng 10 năm 1890”. Boston College Newspapers. ngày 4 tháng 10 năm 1890. Truy cập ngày 6 tháng 9 năm 2020. Trích: "Peas and beans cooked in hard water, containing lime or gypsum, will not boil tender, because these substances harden vegetable caseine. Many vegetables, as onions, boil nearly tasteless in soft water, because all the flavor is boiled out."
Ryznar, J.W.; Langelier, W. F. (tháng 4 năm 1944). “A New Index for Determining Amount of Calcium Carbonate Scale Formed by a Water”. Journal of the American Water Works Association. 36 (4): 472–486. doi:10.1002/j.1551-8833.1944.tb20016.x. JSTOR23345279.
Alsaqqar, Awatif S.; Khudair, Basim H.; Ali, Sura Kareem (2014). “Evaluating Water Stability Indices from Water Treatment Plants in Baghdad City”. Journal of Water Resource and Protection. Scientific Research Publishing, Inc. 06 (14): 1348. doi:10.4236/jwarp.2014.614124. ISSN1945-3094.
American Water Works Association (2003). Water Treatment. Principles and practices of water supply operations series. American Water Works Association. tr. 314. ISBN978-1-58321-230-1.
American Water Works Association (2003). Water Quality. Principles and practices of water supply operations series. American Water Works Association. tr. 125. ISBN978-1-58321-232-5.
Ryznar, J.W.; Langelier, W. F. (tháng 4 năm 1944). “A New Index for Determining Amount of Calcium Carbonate Scale Formed by a Water”. Journal of the American Water Works Association. 36 (4): 472–486. doi:10.1002/j.1551-8833.1944.tb20016.x. JSTOR23345279.
Alsaqqar, Awatif S.; Khudair, Basim H.; Ali, Sura Kareem (2014). “Evaluating Water Stability Indices from Water Treatment Plants in Baghdad City”. Journal of Water Resource and Protection. Scientific Research Publishing, Inc. 06 (14): 1348. doi:10.4236/jwarp.2014.614124. ISSN1945-3094.