Rose, Leo E.The Politics of Bhutan. — Ithaca: Cornell University Press, 1977. — С. 24. — ISBN 0-8014-0909-8.. — «[T]here can be no doubt that since at least the tenth century no external power has controlled Bhutan, although there have been periods when various of its neighbors have been able to exert a strong cultural and/or political influence there.».
Singh, Nagendra. Bhutan, a kingdom in the Himalayas: a study of the land, its people and their government (англ.). — 3rd. — S. Chand[англ.], 1985. — P. 52.
