References – AN 1.188-197: Chapter One 
Sutta / Aṅguttara Nikāya / AN 1: Ekakanipāta / AN 1.188:

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“Why do so many different teachings exist, like Zen, Advaita, or others?” Answered by Ajahn Pasanno. [Spiritual traditions ] // [Human] [Personality] [Great disciples]

Suttas: AN 1.188-267: The qualities of the great disciples.

Thanksgiving Retreat 2010, Session 1, Excerpt 5