“The Effects of Fentanyl or Morphine Added to Intrathecal Bupivacaine in Spinal Anesthesia for Cesarean Section ”. Annals of Medical Research 14, no. 2 (May 25, 2021): 0085–0089. Accessed October 14, 2025. http://annalsmedres.org/index.php/aomr/article/view/3162.