Composite Bat Official Ruling: 
http://www.nfhs.org/content.aspx?id=4052&terms=Baseball+Rules

An Article from The Washington Times:
A Tough Calling – By Jon Siegel, The Washington Times; July 26, 2006

Resource for Umpiring Articles – The Amateur Umpire
http://www.amateurumpire.com/amateurumpire/others/index.htm