Donald S. Lopez, Jr., Rebecca Bloom, Kevin Carr, Chun Wa Chan, Ha Nul Jun, Carla Sinopoli, & Keiko Yokoto-Carter, Hyecho's Journey: The World of Buddhism (Chicago & London: U. of Chicago Press, 2017).
Frederick J. Streng, Emptiness: A Study of Religious Meaning (Nashville & New York: Abingdon Press, 1967).