Hamfelt A., Söderhjelm L. and Mikaelsson G. 1984. Plasma Pyridoxal Phosphate in Women Taking Oral Contraceptives since at Least Five Years. Upsala Journal of Medical Sciences. 89, 3 (Sep. 1984), 285-286. DOI:https://doi.org/10.3109/03009738409179510.