The Monsters Know What They're Doing     Dungeons And Dragons original/official source
Monstrosities     Swords & Wizardry original/official source
Angry Golem (web)     D&D 5e original/official source
Pathfinder 1e Bestiary 2     Pathfinder original/official source
Pathfinder 2e Bestiary 1     Pathfinder original/official source
Forgotten Foes     Pathfinder original/official source
Monster Manual     D&D 5e original/official source
D&D 2e Monstrous Manual     D&D 2e original/official source
Scruffy Grognard's Monstrous Manual     D&D 2e (no source link)
Mystara Adversary Compendium I     Dragon Age original/official source
The Atlantean Bestiary     Any original/official source