Bowen R (24. 1. 1999.). „Vasoactive Intestinal Peptide”. Pathophysiology of the Endocrine System: Gastrointestinal Hormones. Colorado State University. Arhivirano iz originala na datum 2012-02-04. Pristupljeno 6. 2. 2009.
Bowen R (24. 1. 1999.). „Vasoactive Intestinal Peptide”. Pathophysiology of the Endocrine System: Gastrointestinal Hormones. Colorado State University. Arhivirano iz originala na datum 2012-02-04. Pristupljeno 6. 2. 2009.