The Monsters Know What They're Doing     Dungeons And Dragons original/official source
Pathfinder 1e Bestiary 1     Pathfinder original/official source
Pathfinder 2e Bestiary 1     Pathfinder original/official source
Mythic Monster Manual v1     Pathfinder original/official source
Monster Manual     D&D 5e original/official source
Monster Ecology Anthology     D&D 5e (no source link)
Monster Manual 2     D&D 4e (no source link)
Dragon Magazine     D&D 2e/3e (no source link)
MojoBob (web)     D&D 2e 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)
AD&D Monster Manual     AD&D 1e (no source link)
13th Age Bestiary     13th Age original/official source
Dragonlance Bestiary     SAGA (no source link)
Lairs And Encounters     Adventurer, Conqueror, King (no source link)
Baby Bestiary 2     Any original/official source