Saran, A., A. Raipure, R. S. Chauhan, S. Bohra, and S. Bhargava. “Comparison of Intrathecal Isobaric Ropivacaine With Fentanyl and Isobaric Bupivacaine With Fentanyl for Spinal Anesthesia for Lower Abdominal and Lower Limb Surgery”. Anaesthesia, Pain & Intensive Care, Vol. 22, no. 1, Jan. 2019, pp. 38-42, https://apicareonline.com/index.php/APIC/article/view/18.