"Nāgārjuna on Mindfulness of the Buddha" consists of three extended passages from Bhikshu Dharmamitra's original annotated translations from Sino-Buddhist Classical Chinese of works written by Ārya Nāgārjuna (circa 150 ce).
All three of these passages have been selected from Tripitaka Master Kumārajīva's early Fifth Century Sanskrit-to-Chinese translations of works by Nagarjuna, as follows:
1) "The Easy Practice" -- Nāgārjuna's Treatise on the Ten Grounds, Chapter 9;
2) "The Pratyutpanna Samadhi" -- Nāgārjuna's Treatise on the Ten Grounds, Chapters 20-25; and
3) "Recollection of the Buddha" -- Nāgārjuna's Exegesis on the Mahāprajnāpāramitā Sūtra, Chapter 1, Part 36-1"