The great seal of voidness : the root text for the Ge-lug Ka-gyu tradition of Mahamudra, the main path all Buddhas have travelled : together with an oral explanation based on the commentary - Blo-bzaṅ-chos-kyi-rgyal-mtshan, Panchen Lama I, 1567?-1662 (Library of Tibetan Works and Archives, 1975)