Glen of Herding Cat’s was kind enough to upload his briefing which highlights the FIVE Stages of Team Development. Yes, it’s commonly referred to as the “four stages”, but at Glen’s site you’ll find the complete version:
Forming –> Storming –> Norming –> Performing –> Adjourning.
The fifth stage, Glen kindly notes, was later added by original developer Bruce Tuckman.
Check out more here: Forming, Storming, Norming, Performing, and Adjourning