HAU, W.-L., S.-L. TSANG, W. KWAN, L. S.-K. MAN, K.-Y. LAM, L.-F. HO, H.-Y. CHEUNG, F.-K. LAI, C.-Y. LAI, and W. SIN. “The Use of Birth Ball As a Method of Pain Management in Labour”. Hong Kong Journal of Gynaecology, Obstetrics and Midwifery, vol. 12, no. 1, Mar. 2023, doi:10.12809/hkjgom.12.1.125.