1) Bates, Roger G. Determination of pH: theory and practice. Wiley, 1973.
2)Water Treatment Unit Processes: Physical and Chemical
 By David W. Hendricks
3) http://www.thefreedictionary.com/turbidity
4)  "Alkalinity". The WQA Glossary of Terms. 31 March 2000. Retrieved 6 March 2013.
5) hard water. (n.d.). Dictionary.com Unabridged. Retrieved October 19, 2014, from Dictionary.com website: http://dictionary.reference.com/browse/hard water