March 13, 2012 8:52 pm
- Aguilar, N. (1986). The new no-pill, no-risk birth control. New York: Macmillan.
- Couple to couple league (2005). Marital duration and natural family planning.
- Wilson, M. A. “The use of natural family planning versus the use of artificial birth control: Family, sexual and moral issues.” Catholic Social Science Review 7 (2002)., 1-20. Available online but difficult to locate.