The Monsters Know What They're Doing     Dungeons And Dragons original/official source
Angry Golem (web)     D&D 5e original/official source
OSE Encounter Activity Tables     Any original/official source
Pathfinder 2e Bestiary 2     Pathfinder original/official source
Monster Manual     D&D 5e (no source link)
Monster Monday (web)     D&D 5e original/official source
Monster Ecology Anthology     D&D 5e (no source link)
Scruffy Grognard's Monstrous Manual     D&D 2e (no source link)
Dragonlance Bestiary     SAGA (no source link)
Hacklopedia Of Beasts     Hackmaster (no source link)