Cicero. (2023, October 21). Wikiquote. Retrieved January 1, 2024 from https://en.wikiquote.org/w/index.php?title=Cicero&oldid=3384264.
She also notes that: “Studies conducted by Elmer and Alyce Greene at the Menninger Foundation have shown that a subject with 20 years of training in Zen meditation could consistently establish Hemi-sync at will, sustaining it for over 15 minutes.