Mathes, Klaus-Dieter (2015a): The Pith Instructions on the Mahāyāna Uttaratantra (Theg chen rgyud bla’i gdams pa) – A Missing Link in the Meditation Tradition of the Maitreya Worksiehe In: Czaja / Hazod: The Illuminating Mirror.- Wiesbaden: Reichert. (Contributions to Tibetan Studies.12)