Pokémon Yellow's Biggest Pokédex Changes From Red & Blue

Pokémon Yellow was an updated version of Red and Blue in many ways, including the Pokédex, which holds some stark differences from its predecessors.

Pokémon Blue Version (Japanese) - Bulbapedia, the community-driven Pokémon encyclopedia

25 Hidden Secrets Many Fans Still Haven't Found In Pokémon Red/Blue/Yellow

Pokemon Red, Blue, and Yellow Version Differences - Pokemon Red, Blue and Yellow Guide - IGN

Here is a map I made with the location and info for all catchable Pokemon in Red, Blue and Yellow in celebration of the 20th anniversary. : r/pokemon

Pokémon Red and Green Versions - Bulbapedia, the community-driven Pokémon encyclopedia

Generation I, Pokémon Wiki

Red, Blue & Yellow Pokédex

Pokedex - Pokemon Red, Blue and Yellow Guide - IGN

Pokémon Red & Blue