References – SN 12.38: Volition (1) 
Readings by Ajahn Pasanno:
Sutta: SN 22.53, Khandhasaṁyutta, “Engagement.”
Sutta: SN 22.54, Khandhasaṁyutta, “Seeds.”
Sutta: MN 22.36.
Sutta: SN 12.64.
Sutta: Snp 758-759.
Sutta: SN 12.38.
Skill in Questions by Ajahn Ṭhānissaro p. 349.
Reading about Luang Por Dun (similar to Gifts He Left Behind by Ajahn Dune, p. 77).
The Fourth Foundation of Mindfulness [2013], Session 36
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.