Original: The Tibetan representatives who signed this document were Agvan Dorjiev, a Buryat, i.e. citizen of Russia, Chijamts, and Gendun-Galsan a Tibetan citizen.
Simplified: Those who signed for Tibet were Agvan Dorjiev, Chijamts, and Gendun-Galsan, who lived in Tibet. Dorijev was  a Buryat, a citizen of Russia.