http://www.stanford.edu/~atkins/swatch. swatch home page. (Has links to the latest version, online manpages, etc.)
http://www.stanford.edu/~atkins/swatch/lisa93.html. Hansen, Stephen and Todd Atkins, creators of swatch. "Centralized System Monitoring with Swatch." (Old, but still useful.)
http://www.enteract.com/~lspitz/swatch.html. Spitzner, Lance. "Watching Your Logs." (A brief introduction to swatch.)
Friedl, Jeffrey E. F. Mastering Regular Expressions. Sebastopol, CA: O'Reilly & Associates, Inc. 1998.