9. ULTRASOUND-ASSISTED SPINAL ANESTHESIA AT L5-S1 IN PATIENTS WITH ANKYLOSING SPONDYLITIS. YHCĐ [Internet]. 2024 Sept. 26 [cited 2026 Sept. 9];65(CĐ 9 - Hội Gây mê Hồi sức). Available from: https://tapchiyhcd.vn/index.php/yhcd/article/view/1516