Low free testosterone and prostate Cancer risk: a collaborative analysis of 20 prospective studies. Watts, E.L., Appleby, P.N., Perez-Cornago, A., Bueno-de-Mesquita, H.B., Chan, J.M., Chen, C., Cohn, B.A., Cook, M.B., Flicker, L., Freedman, N.D. … G.J… and Giles, G.G., 2018. European urology, 74(5), pp.585-594.