Pongsri, Wichuda, Kamonchanok Phuob, and Supawat Simsiriwat. 2019. “Optimal dose of intrathecal morphine used for cesarean delivery anesthesia: a systematic review”. The Clinical Academia 42 (6):240-49. https://he02.tci-thaijo.org/index.php/theclinicalacademia/article/view/172239.