See the Tibetan translation of the Sarasvatīvyākaraṇa by Si tu paṇ chen Chos kyi ’byung gnas (i.e. mTso ldan ma’i brda sprod pa’i rab byed. Bod kyi bcu phrag rig mdzod chen mo: bKa’ brgyud pa’i gsung rab. Lanzhou: Kan su’u mi rigs dpe skrun khang, 2004, vol. 1, p. 286: spyi bor thig le ni rjes su nga ro’o ||. I assume that spyi bor thig le is rendering of śīrṣabindu. But is śīrṣabindu as a name for the anusvāra sign attested in Sanskrit sources?
