The Monsters Know What They're Doing     Dungeons And Dragons original/official source
OSE Encounter Activity Tables     Any original/official source
Monster Menagerie: Kith Of The Harpy Queen     Pathfinder original/official source
Monster Manual     D&D 5e (no source link)
Flee, Mortals     D&D 5e (no source link)
Old Gus: Plantfolk, Undead, And Other Oddities     D&D 5e original/official source
Monster Ecology Anthology     D&D 5e (no source link)
Monster Manual     D&D 4e (no source link)
Scruffy Grognard's Monstrous Manual     D&D 2e (no source link)
AD&D Monster Manual     AD&D 1e (no source link)
Monsters Compendium     Heroes Of Adventure (no source link)
Godforsaken     Cypher System (no source link)
Monsters: A field Guide     HARP (no source link)
The Monster Overhaul     OSR (no source link)
Lairs And Encounters     Adventurer, Conqueror, King (no source link)