Edwin G. Pulleyblank
This "Fan" 蕃 pronunciation of "B'i̭wan" illustrates the difference between modern Chinese pronunciation and the Middle Chinese spoken during the Sui Dynasty (581-618 CE) and Tang Dynasty (618-907 CE) period when "Tibet" was first recorded. Reconstructed Middle Chinese pronunciations of "Tǔbō" and "Tǔfān" "Tibet" are: "t'uopuâ" and "t'uop'i̭wɐn" (Bernhard Karlgren), "thwopwâ" and "thwobjwɐn" (Axel Schuessler), "tʰɔ'pa" and "tʰɔ'puan" (Edwin G. Pulleyblank "Early Middle"), or "thuXpat" and "thuXpjon" (William H. Baxter)