Voice Command Reference
http://www.cisco.com/en/US/docs/ios/voice/command/reference/vr_book.html
http://www.ciscosystems.info/en/US/docs/ios/12_3t/voice/command/reference/123tvr.html
Configuration Library
http://www.cisco.com/en/US/docs/ios/12_3/vvf_c/cisco_ios_voice_configuration_library_glossary/vcl.htm
Troubleshooting and Monitoring Guide
http://www.cisco.com/en/US/docs/ios/12_3/vvf_c/voice_troubleshooting/old/voipt_c.html