Johns12, Helene M; Forster, Della A; Amir1, Lisa H; McLachlan, Helen L (19 november 2013). BMC Pregnancy and Childbirth 13: sid. 212. doi:10.1186/1471-2393-13-212. PMID 24246046.
Johns12, Helene M; Forster, Della A; Amir1, Lisa H; McLachlan, Helen L (19 november 2013). BMC Pregnancy and Childbirth 13: sid. 212. doi:10.1186/1471-2393-13-212. PMID 24246046.