Halkias, 'Phang thang, p. 56. Brother of Khri lde srong btsan, he was not allowed to rule because of his murder of 'U rings, the son of Zhang Rgyal tshan lha snang in around 794-796 CE. However, the T'ang annals recognize that "he" (some Tibetan emperor or another) reigned until his death in 804 CE.
The 'Phang thang ma is the only known Tibetan source that explicitly names him as one of the emperors (which would mean he was expunged from the dynastic succession records). Later sources say he was killed by a Sna nam family member because he killed Sna nam 'U rings, son of Sna nam Rgyal mtshan lha snang. Brandon Dotson, "Emperor" Mu rug btsan and the 'Phang thang ma Catalogue, Journal of the International Association of Tibetan Studies, no. 3 (December 2007), pp. 1-25.
Bibliography:
'Phags pa dgongs pa nges par 'grel pa'i mdo bshad pa.
