Waddell, Lhasa and its Mysteries (1905), p. 80: "we marched up the valley, to the village of Chumbi, which has given the valley the name by which it is known to Europeans..." Waddell, L. Austin (1905), Lhasa and its Mysteries, London: John Murray – via archive.org
Karan, Bhutan: A Physical and Cultural Geography (1967), p. 9, "To the southwest of Chomo Lhari, the western slopes of the Khungdugang mountain and Merug La separate Bhutan from the Chumbi valley of Tibet. To the north of Merug La the Torsa river (known as the Amo Chu) cuts across the international boundary." Karan, Pradyumna P. (1967), Bhutan: A Physical and Cultural Geography, University of Kentucky Press, LCCN67-17842 – via archive.org
Banerji, Arun Kumar (2007), "Borders", in Jayanta Kumar Ray (ed.), Aspects of India's International Relations, 1700 to 2000: South Asia and the World, Pearson Education India, p. 196, ISBN978-81-317-0834-7
Karan, Bhutan: A Physical and Cultural Geography (1967), p. 9, "To the southwest of Chomo Lhari, the western slopes of the Khungdugang mountain and Merug La separate Bhutan from the Chumbi valley of Tibet. To the north of Merug La the Torsa river (known as the Amo Chu) cuts across the international boundary." Karan, Pradyumna P. (1967), Bhutan: A Physical and Cultural Geography, University of Kentucky Press, LCCN67-17842 – via archive.org