Chaemsaithong, Piya, Kasem Raungrongmorakot, and Patama Promsonthi. 2012. “Progesterone for Prevention of Preterm Birth”. Thai Journal of Obstetrics and Gynaecology 20 (4). Bangkok, Thailand:222-30. https://he02.tci-thaijo.org/index.php/tjog/article/view/4692.