大般涅槃經義記 4.89

4.89

若以諸字盡具相配入十二音，通合應有三十六章，不能煩廣，略舉斯耳。

If all the letters were fully combined with each other into the twelve sounds, there should altogether be thirty-six charts; unable to go into such burdensome breadth, they are merely outlined here.