1. Efficacy of methods for determining ovulation in a natural family planning program 
Maurizio Guida, M.D., Giovanni A Tommaselli, M.D., Stefano Palomba, M.D., Massimiliano Pellicano, M.D., Gianfranco Moccia, M.D., Costantino Di Carlo, M.D., Carmine Nappi, M.D. 
Fertility and Sterility 
Volume 72, Issue 5, Pages (November 1999)
DOI: /S (99)

2. Figure 1
Timing of ovulation as determined by the different methods throughout a 12-day periovulatory period. ♦ = urinary LH kit; ■ = β-glucuronidase level determination; ▴ = salivary ferning test; × = determination of mucus characteristics; ∗ = BBT measurement.
Guida. Determining ovulation. Fertil Steril 1999.
Fertility and Sterility  , DOI: ( /S (99) )