G* power is a free statistical software that allows the user to determine the sample size needed based on a wide variety of tests.
Fundamentals of estimating sample size
How can I do if the sample size generated from G* Power is very
Sample size formula for the comparison of two independent means
The 20% Statistician: Feasibility Sample Size Justification
Calculating Sample Size: Cohen's Tables and G. Power - ppt download
Power Analysis Precision Consulting, LLC
Power and Effect Size
Determining Sample Size in Experimental Studies
How To Determine Sample Size From G*Power
OpenEpi - Sample Size for Unmatched Case-Control Studies
G*Power - One-way between group ANOVA minimum sample size