Qu, J., J. Yang, M. Chen, L. Cui, T. Wang, W. Gao, J. Tian, and R. Wei. “MicroRNA-21 As a Diagnostic Marker for Hepatocellular Carcinoma: A Systematic Review and Meta-Analysis: MiR-21 in HCC”. Pakistan Journal of Medical Sciences, Vol. 35, no. 5, Aug. 2019, doi:10.12669/pjms.35.5.685.