W, A. ., B. . K, N. C, S. L, and P. R. “Cut Off Point of Percentage of Free PSA That Optimize for Prostate Cancer Detection”. Insight Urology, vol. 27, no. 2, Dec. 2006, pp. 73-80, https://he02.tci-thaijo.org/index.php/TJU/article/view/253540.