ParulP.ChristianParulP., Keith PK.P.WestKeith PK.P., jr., Interactions between zinc and vitamin A: an update, „The American Journal of Clinical Nutrition”, 68 (2), 1998, s. 4355–4415, DOI: 10.1093/ajcn/68.2.435S, PMID: 9701158(ang.).
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ParulP.ChristianParulP., Keith PK.P.WestKeith PK.P., jr., Interactions between zinc and vitamin A: an update, „The American Journal of Clinical Nutrition”, 68 (2), 1998, s. 4355–4415, DOI: 10.1093/ajcn/68.2.435S, PMID: 9701158(ang.).