Kaur, J., A. C. Swami, A. Sharma, and A. Sharma. “Continuous Spinal Anesthesia in a Patient With Ankylosing Spondylitis for Total Hip Replacement”. Anaesthesia, Pain & Intensive Care, Jan. 2019, pp. 224-6, https://apicareonline.com/index.php/APIC/article/view/261.