E.H. Angle introduced his classification of malocclusion in:

ANGLE'S CLASSIFICATION OF MALOCCLUSION In 1899, Edward Angle classified malocclusion based on the mesial-distal relation of the teeth, dental arches and jaws. He considered the maxillary first permanent molar as a fixed anatomical point in the jaws and the key to occlusion. Ref: Textbook of orthodontics Gurkeerat Singh 2nd ed page no 163