 The director, in the commentary on the DVD, says that he was  inspired by the book "Caravan Towards Buddha" by Andre Migot. This  book was titled "CARAVANE VERS BOUDDHA" when it was published in  1954, but can now only be found under its alternate (English) title,  "Tibetan Marches" (translated by Peter Fleming). See also "Au Tibet  sur les traces du Bouddha (Collection Itinéraires)" by André Migot.