Altering Cave - Pokemon Fire Red and Leaf Green Guide - IGN

Found north of Sixth Island, this cave only have Zubats. However, if you have an E-reader connected to a gameboy advance using Japanese E-reader cards

Altering Cave - Bulbapedia, the community-driven Pokémon encyclopedia

Appendix:FireRed and LeafGreen walkthrough/Section 16 - Bulbapedia

Pokémon FireRed and LeafGreen/Cerulean Cave — StrategyWiki

Mystery Gift - Pokemon Fire Red and Leaf Green Guide - IGN

Seafoam Islands - Pokemon Fire Red and Leaf Green Guide - IGN

Diglett's Cave - Pokemon Red, Blue and Yellow Guide - IGN

Pokémon Emerald Version - Bulbapedia, the community-driven Pokémon

Pokemon LeafGreen Version [Walkthroughs] - IGN

Celadon City - Pokemon Fire Red and Leaf Green Guide - IGN

Three Island - Pokemon Fire Red and Leaf Green Guide - IGN

Seafoam Islands - Pokemon Fire Red and Leaf Green Guide - IGN

Three Island - Pokemon Fire Red and Leaf Green Guide - IGN