From Gentoo Wiki
- Overlays project - The official Gentoo project for ebuild repositories' support.
- Overlays guide (Overlay project) - A user guide written by the Overlay project.
- Developer's guide to Gentoo overlays - This document is kept only for historical purposes. The current guide is maintained as Project:Overlays/Overlays guide.
- Defining a custom repository - Section in the Gentoo Handbook