CCNP CIT Exam Cram 2 (Exam Cram 642-831)

CCNP BCMSN Exam Cram 2 , Que, 2003, Richard Deal, ISBN: 0-7897-2991-1

Cisco CCO: Troubleshooting STP, http://www.cisco.com/en/US/customer/tech/tk389/tk621/technologies_tech_note09186a0080136673.shtml