evidence: Nepal considers east of the river to be its territory based on the 1816 Sugauli Treaty signed with British colonial rulers. [...] The Sugauli Treaty remains, for Nepal, the "mother of all documents", Upadhyay said, according to which the Mahakali is the boundary river between the two countries, and any future demarcations will be based on the treaty. [...] Most of the 1,751km-long Nepal-India border has been demarcated through a joint boundary committee except for Kalapani and Susta, which lies in southern Nepal.