Sheet 21 SW [First Edition] 1905. Season 1904-05. Surveyed Maj C H D Ryder RE & Capt H Wood RE, and Ram Singh. Published July 1905. Heliozincographed OTB SI Dehra Dun. No.D.34, S.I. 4-5-05.–242. Reg.No.226–S. 05. Incomplete: area of Tsa Chu river only. Printed black and brown; river hand-coloured.