How Do You Unsubdivide A Model In Blender? – blender base camp
Subdivide
Blender Tutorial - Undo, Redo and Repeat Operations for Modeling - YouTube
Andrew Price on Twitter: "Using Blender from 2004. Wow, I've taken so many features for granted! Undo! Modifier stack! Scale to axis! How did we live?! #b3d https://t.co/dCnLEhbe7U" / Twitter
Working with Tools
modeling - Is there an unsubdivide function in Blender? - Blender Stack Exchange