cf. lde'u chos 'byung rgyas pa [1987] (pp. 256-261)
an overview of the administrative yul sde/ (or yul dpon tsan/) districts of the Four Horns acc. to lde'u chos 'byung rgyas pa [1987] and padma bka' thang [mst] (i.e. rgyal po'i bka' thang / ) is found in Dotson & Hazod 2009 (p. 209)
on the term yul sde/, see Dotson & Hazod 2009 (p. 261)