Choavaratana, R., K. Malakorn, I. Thanaboonyawat, S. Petyim, P. Laokirkkiat, N. Saad, and J. Prechapanich. “Endometrial Thinning After Ovarian Stimulation Using Letrozole or Clomiphene Citrate: A Randomized Trial”. Siriraj Medical Journal, vol. 70, no. 4, Nov. 2018, pp. 335-42, https://he02.tci-thaijo.org/index.php/sirirajmedj/article/view/153930.