The Monsters & Creatures Compendium     Any (no source link)
The Monsters Know What They're Doing     Dungeons And Dragons original/official source
Atlas Animalia     Any original/official source
Monster Manual     D&D 5e original/official source
Old Gus: Plantfolk, Undead, And Other Oddities     D&D 5e original/official source
Monster Ecology Anthology     D&D 5e (no source link)
Monster Manual 2     D&D 4e (no source link)
Scruffy Grognard's Monstrous Manual     D&D 2e (no source link)
The Monster Overhaul     OSR (no source link)
Baby Bestiary 2     Any original/official source