Horse caravans were once the main transport in Yunnan, not only providing a regional transport system, but also carrying culture and power.
History of the use of cowries as currency in Yunnan.
Oral history of the Yunnan Caravan trade.
L'Evolution Du System Postal: La Province Chinoise Du Yunnan A L'\`Epoque Qing (1644-1911)
An encyclopedia of old road, bridges and carvavan stops in Yunnan.