Three types of "tantra of words": a] Tantra manifest as sound (sgrar snang ba'i rgyud) is mind transmission or both the transmission of mind and symbol. b] Tantra uttered as sound (sgrar grags pa'i rgyud) is oral transmission of great masters. c] Tantra turned into symbols (brdar gyur pa'i rgyud) is the letter characters of the scriptures. For example, the terma teachings belong to the category of the three types of tantra of words; the mind transmission is to keep in mind what he initially have heard, the oral transmission he uttered it to the King and the subjects as the spontaneous sound of dharmata, and the Word Transmission of Yellow Parchment (shog ser tshig brgyud) is the teaching written down on the yellow parchment