To what extent can Ānāpānasati be related to Vipassanā? I've read that the two can somehow be used in Unison, with benefit. Can anyone expand on this?
Anapanasati is divided into 4 tetrads which correspond to the 4 Satipatthana hence the pratice of Anapanasati is actually a forms of Satipatthana / Vipassana. A thorough introduction to Anapanasati and how to develop this into Vipassana is difficult in this format hence it might be worthwhile to read a more elaborate book on it: Anapanasati: Mindfulness of Breathing by Buddhadasa Bhikkhu. You can complement this book with: Right Mindfulness: Memory &amp; Ardency on the Buddhist Path by Thanissaro Bhikkhu