Mdo khams chu drug sgaṅ lṅaʼi gźi gter gnas bdag yul lha rgya mtshoʼi bsaṅ mchod lha srin dgyes paʼi mchod sprin : a collection of instructions for offering bsaṅs to the various local deities of eastern Tibet and specifically the Lha-thog and Naṅ-chen areas