git-add(1) Manual Page, Git Developers, 2024 - Official documentation for the git add command, detailing its usage and options.
Pro Git, Scott Chacon and Ben Straub, 2024 (Apress) - An authoritative book covering Git fundamentals, including the staging area and the git add command.
Git Glossary, Git Developers, 2024 - Official Git glossary providing definitions for core Git concepts like 'index' and 'staging area'.