"Journal of Perinatal Medicine - Official Journal of the WAPM", 18.s1 (1990): 7-127. Retrieved 23 May. 2013, from http://www.degruyter.com/view/j/jpme.1990.18.issue-s1/issue-files/jpme.1990.18.issue-s1.xml

Journal of Perinatal Medicine - Official Journal of the WAPM (1990), 18(s1), pp. 7-127. Retrieved 23 May. 2013, from http://www.degruyter.com/view/j/jpme.1990.18.issue-s1/issue-files/jpme.1990.18.issue-s1.xml

Journal of Perinatal Medicine - Official Journal of the WAPM. 1990. 18(s1): 7-127. Retrieved 23 May. 2013, from http://www.degruyter.com/view/j/jpme.1990.18.issue-s1/issue-files/jpme.1990.18.issue-s1.xml