PT Journal AU Joffe, M TI Methods for obtaining valid data on time to pregnancy among men and women SO Scandinavian Journal of Work, Environment & Health PD VL PY 1999 BP 8 EP 9 IS 1 WP https://www.sjweh.fi/show_abstract.php?abstract_id=388 DE fertility; subfecundity; validity SN 0355-3140 ER