Buddha is without beginning, middle, or end. He is peace itself, fully self-awakened and self-expanded in buddhahood.
Having reached this state, he shows the indestructible, permanent path so that those who have no realization may realize.
Wielding the supreme sword and vajra of knowledge and compassionate love, he cuts the seedling of suffering and destroys the wall of doubts along with its surrounding thicket of various views. I bow down to this Buddha. ~ Arya Maitreya
Gyumed Khensur Rinpoche Lobsang Jampa (Do Ngak Kunphen Ling) gave an informative and inspiring weeklong teaching on the singularly important Buddhist philosophical work entitled The Treatise on the Higher Doctrine of the Great Vehicle (S: Mahāyānottaratantraśāstra, T: Theg pa chen po rgyud bla ma’i bstan bcos), which is also known by the name Distinguishing the Spiritual Lineage of the Three Jewels (S:Ratnagotravibhāga, T: dKon mchog gi rigs rnam par dbye ba).
Dr. Art Engle did a masterful job of translating for Rinpoche. The teachings are now available on YouTube.
Buddha Nature: The Mahayana Uttaratantra Shastra with Commentary. commentary by Jamgon Kongtrul Lodro Thaye; explanations by Khenpo Tsultrim Gyamtso Rinpoche. Snow Lion: 2000.
https://www2.hf.uio.no/polyglotta/index.php?page=fulltext&vid=61&view=fulltext – root text with Indian commentary attributed to Asanga. English, Chinese, Tibetan phonetics only
http://www.dminamart.com/index.php/tibetan-buddhist/92-gyud-lama — root text (Tibetan only)
Root text is also available from https://www.tbrc.org search for: ཐེག་པ་ཆེན་པོ་རྒྱུད་བླ་མའི་རྩ་བ་བཞུགས་སོ
Background reading for this subject
Familiarity with the Prajnaparamita teachings is helpful as a foundation for understanding Uttaratantra. This is a good overview: The Ornament of Clear Realization by Maitreya commentary by Khenchen Thrangu Rinpoche Zhysil Chokyi Ghatsal Charitable Trust Publication: 2004.