Billings, E. 9 Mengajar Metode Ovulasi Billings. Kanisius.
Chicago Style (17th ed.) CitationBillings, E. 9 Mengajar Metode Ovulasi Billings. Kanisius.
MLA (8th ed.) CitationBillings, E. 9 Mengajar Metode Ovulasi Billings. Kanisius.
Warning: These citations may not always be 100% accurate.