RT Journal Article SR Electronic T1 Proceedings: Cyclic variation of obstetric phenomena in Cardiff. JF British Journal of Preventive & Social Medicine JO Br J Prev Soc Med FD BMJ Publishing Group Ltd SP 66 DO 10.1136/jech.28.1.66-b VO 28 IS 1 A1 C J Roberts A1 S Lloyd YR 1974 UL http://jech.bmj.com/content/28/1/66.3.abstract AB