The four establishments of mindfulness and its sutta history - as well as the Bhikkhunupassaya Sutta - Directed and Undirected Meditation (SN: 47:10). Suttas available here: https://a-buddha-ujja.hu/sn-47.3/en/bodhi) and here https://www.accesstoinsight.org/tipitaka/sn/sn47/sn47.010.olen.html