References – SN 12.38: Volition (1) 
Readings by Ajahn Amaro:
The Island by Ajahn Pasanno and Ajahn Amaro, Chapter 8, pp. 146-150:
Ajahn Chah, (anecdotal).
Atulo, collected teachings of Ajahn Dune compiled by Ajahn Bodhinandamuni (no full English translation).
Suttas: MN 49.25; SN 12.38; SN 22.53.
Suttas: MN 49.11-31; MN 140.21-22.