役に立つサイト Some sites that may be useful to predict ovulation.

排卵検査薬 (Japanese)
http://prematernity.web.fc2.com/hairan/hairan-2.html

http://ovulations.info/

Useful sites for predicting ovulation. (English)

http://www.babymed.com/fertility-ovulation-calendar-calculator

http://www.wikihow.com/Calculate-Your-Ovulation

http://www.wikihow.com/Determine-Your-Most-Fertile-Day-to-Conceive

http://www.wikihow.com/Work-out-Ovulation-With-Irregular-Periods