1. The association between vasectomy and prostate cancer: a systematic review of the literature 
Enrique Bernal-Delgado, Ph.D., Jaime Latour-Pérez, Ph.D., Félix Pradas-Arnal, M.D., Luis I. Gómez-López, Ph.D. 
Fertility and Sterility 
Volume 70, Issue 2, Pages (August 1998)
DOI: /S (98)

2. FIGURE 1
Individual risks and overall effect calculated by the DerSimonian and Laird method. LnRR = risk ratio logarithm. Hsing et al. have three kinds of controls: cancer controls, noncancer controls, and population controls.
Fertility and Sterility  , DOI: ( /S (98) )

3. FIGURE 2
Impact of heterogeneity on the overall effect (DerSimonian and Laird method). (A), Study setting. (B), Study design. (C), Inadequate control selection. (D), Detection bias.
Fertility and Sterility  , DOI: ( /S (98) )

4. FIGURE 3
Evaluation of publication bias (funnel plot). LnRR = risk ratio logarithm.
Fertility and Sterility  , DOI: ( /S (98) )