Thai is a member of the Tai family of languages, which are spoken by an estimated 70 million people dispersed over a wide area of Asia, from northern Vietnam to Northern India. There are many ways of romanising Thai but no universally recognised system. Academic linguists use one system, librarians another, the Royal Thai Institute yet another, while writers of textbooks, phrasebooks and dictionaries often adapt or devise their own personal systems. Thai's can neither systematically write their language in the Western alphabet nor easily read Westerners' romanisations of Thai; the average Thai, when called upon to romanise Thai words, will almost certainly do so in a quite unsystematic way. There is a rich English-language literature on many aspects of Thai linguistics, most of which is catalogued in Franklin E. Huffman's Bibliography and Index of Mainland Southeast Asian Languages and Linguistics.