Other
Lake Tahoe Community College
This site offers a clear definition of what a Power Series is and clearly discusses the radius of Convergence using the ratio test through clear examples.
Department of Defense
Do Dea: Convergence Tests Summary and Study
Here is a summary of convergence tests. They are listed in the order that you should use/try them when testing for convergence or divergence.
Other
Sierra College: Summary of Tests for Series
Provides a summary of tests for series that includes the test, series, converges, sum of remainder, and diverges for nth Term, Geometric Series, Telescoping Series, p-Series, Alternating Series, Integral, Root, Ratio, Direct Comparison,...
Math Open Reference
Math Open Reference: Series
A complete reference guide to a series. It provides definitions, examples, and an animation that enhances further explanation. Includes links to related topics.