Other
Ibm: Mastering Recursive Programming
A discussion of how to write a correct recursive algorithm. Numerous examples are given in several different programming languages.
National Institute of Standards and Technology (NIST)
Dictionary of Algorithms and Data Structures: Recursion
The DADS description of recursive algorithms in computer programming.
Wikimedia
Wikipedia: Recursion
A Wikipedia description of the use of recursion in computer programming, including several examples in different programming languages.