Retrieved 31 December 2014. Cite book URL http://whqlibdoc.who.int/publications/2004/9241546123.pdf Title Vitamin and mineral requirements in human nutrition Date 2004 Publisher World Health Organization ISBN 9241546123 Edition 2nd Page 138 URL access date 31 December 2014 ↑ Gropper SS, Smith JL, Grodd JL (2004). Advanced Nutrition and Human Metabolism (4th ed.).