OpenEpi:Sample Size for X-Sectional,Cohort,and Clinical Trials
Sample size calculation for small sample single-arm trials for time-to-event data: Logrank test with normal approximation or test statistic based on exact chi-square distribution? - ScienceDirect
PS: Power and Sample Size Calculation 3.0 Download (Free) - PS.exe
Improved Sample Size Calculator Website and New Calculators for Your Research | Clinical & Translational Science Institute