Waterfall Used, 1991 – Department of Defense: Capabilities Maturity Model (O-25) [pdf](apps.dtic.mil)
apps.dtic.mil
Waterfall Used, 1991 – Department of Defense: Capabilities Maturity Model (O-25) [pdf]
https://apps.dtic.mil/sti/tr/pdf/ADA240604.pdf
https://apps.dtic.mil/sti/tr/pdf/ADA240604.pdf
"'For those who use the waterfall life-cycle model, the term 'stage' is equivalent to 'phase'".