Ikhsan Tri Kurnia and Dewi Wijaya, “Vitamin D Supplementation Efficacy in Severe Vitamin D-Deficient versus Insufficient COPD Patients: A Stratified Meta-Analysis of Exacerbation Risk”, Bioscmed, vol. 10, no. 3, pp. 988–1001, Jan. 2026, doi: 10.37275/bsm.v10i3.1545.