Cass H, Gringras P, March J, McKendrick I, O'Hare AE, Owen L, Pollin C (2008): «Absence of opioid peptides in children with autism» PMID 18337276. Fri fulltekst (HTML).
Dettmer K, Hanna D, Whetstone P, Hansen R, Hammock BD (2007): «Autism and urinary exogenous neuropeptides: development of an on-line SPE-HPLC-tandem mass spectrometry method to test the opioid excess theory» PMID 17520243
Cass H, Gringras P, March J, McKendrick I, O'Hare AE, Owen L, Pollin C (2008): «Absence of opioid peptides in children with autism» PMID 18337276. Fri fulltekst (HTML).
web.archive.org
«NCF». Arkivert fra originalen 12. april 2021. Besøkt 18. mars 2021.