Nicolson. 2001 [2000]. ISBN 978-0-7538-1130-6. Vail Motter, T. H. The PersianCorridor and Aid to Russia. Washington, DC: U.S. Government Printing Office
" The long stretch from the Kabul River to China, including the Wakhan Corridor, was declared demarcated by virtue of its continuous, distinct watershed
barbarian from the general area of the Eurasian steppe, the virtually treeless corridor of drought-resistant perennial grassland extending from the Danube to Manchuria