1. J M Pelczar, E C S Chan and N R Krieg, Microbiology (McGraw-Hill, New York, 1986)
2. I L Pepper, C P Gerba and J W Brendecke, Environmental microbiology — A laboratory manual (Academic Press, San Diego, CA, 1995) pp. 67–127
3. J P Duguid, B P Marmion and R H Swain, Mackie and McCartney medical microbiology (ELBS/Churchill Livingstone, Edinburgh, 1978) Vol. 1
4. L M Prescott, J P Harley and D A Klein, Microbiology (WCB McGraw-Hill, 1999) Chap. 2, 15, 32, 41
5. K Kerman Kobayashi and E Tamiya, Meas. Sci. Technol. 15, R1 (2004)