Referenced In

The Travels of Marco Polo
by Marco Polo, da Pisa Rusticiano

"Just at the skirt of this mountain region, where the great road to Lhása enters it, lies the large and bustling city of Yachaufu, forming the key of the hill country, and the great entrepôt of trade between Sze-ch’wan on one side, and Tibet and Western Yunnan on the other."