Widarti R. PENERAPAN WILLIAM FLEXION EXERCISE PADA KASUS NYERI PUNGGUNG BAWAH (LOW BACK PAIN). Gemassika [Internet]. 2018 May 30 [cited 2024 Jul. 3];2(1):28-31. Available from: https://journal.aiska-university.ac.id/index.php/gemassika/article/view/252