The Relative Strength Index by Bruce Faber
Here's a primer on the relative strength index, which helps identify market reversals and trends.
The relative strength index (RSI), which was created by J. Welles Wilder, was first presented in his New Concepts in Technical Trading Systems. It is a popular indicator among traders and can be found in many technical software packages. It is, first of all, a momentum indicator of an individual stock, commodity or market index; it does not measure a comparison of one stock relative to another stock or market index, such as the relative strength ranking used by Investor's Business Daily. The indicator compares an equity only with its own past performance. The RSI is most widely used among traders of commodities and futures.