Iftikhar, Afshan, et al. “ASSOCIATION OF SERUM P1NP (N-TERMINAL PROPEPTIDE OF TYPE1 COLLAGEN) AND BONE MINERAL DENSITY (BMD) IN OSTEOPOROSIS: BMD And P1NP”. Pakistan Armed Forces Medical Journal, vol. 68, no. 2, Apr. 2018, pp. 357-62, https://www.pafmj.org/PAFMJ/article/view/1461.