References – Ud 7: The Lesser Chapter 
Sutta / Udāna / Ud 7: Cūḷavagga
Udāna 7.8: Kaccāna 

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Readings by Ajahn Pasanno: [Mindfulness of breathing] [Mindfulness of body]

Right Mindfulness pp. 115-119.

Sutta: MN 80: Vekhanassa Sutta, To Vekhanassa.

Sutta: Ud 7.8: “Kaccāna.”

Sutta: MN 62: Mahārāhulaovāda Sutta, The Greater Discourse of Advice to Rāhula.

The Four Foundations of Mindfulness [2015], Session 36