By: The Numata Center
Contains On the Differences Between the Exoteric and Esoteric Teachings; The Meaning of Becoming a Buddha in This Very Body; The Meanings of Sound, Sign, and Reality; The Meanings of the Word Hum; and The Precious Key to the Secret Treasury by Kukai and The Mitsugonin Confession; and The Illuminating Secret Commentary on the Five Cakras and the Nine Syllables by Kakuban.
BDK English Tripitaka 98-I, II, III, IV, V, VI, VII.