On the LibraryThing page for Charles Duff I noticed that alongside Russian for Beginners, the book from which I taught myself Russian, were listed German for Beginners, Spanish for Beginners, French for Beginners, and Italian for Beginners (not to mention A Handbook On Hanging: Being A Short Introduction To The Fine Art Of Execution). How did this guy manage to write textbooks for all those languages? Who was Charles Duff? Well, there’s not a whole lot on the internet, but the NYRB (which republished the hanging book) says “Charles Duff (1894-1966) served as an officer in the British Merchant Navy during World War I and then in the intelligence division of the Foreign Office and Diplomatic Service. After retiring, he taught linguistics and languages in London and Singapore while writing travel guides, histories, satires, and a series of text books.” And this Spanish book catalog (pdf) suggested that Carlos Prieto, author of Spanish Front (1936), was a “posible seudónimo de Charles Duff,” which led me to this page of Prieto books, where a copy of Spanish Front is described as “Inscribed To David from Carlos Prieto (Anglican Charles Duff) 8/7/37″—I assume “Anglican” is a misunderstanding of anglicè ‘in English,’ which would tend to support the pseudonym theory. And the first page (all you can read without a JSTOR subscription) of the Oct. 1948 review by Robert J. Clements in The Modern Language Journal of Duff’s 1947 book How to Learn a Language adds more information: Duff “for many years trained language teachers at the University of London” and “was active for eighteen years in the Foreign Office and is author of a series of seven basic and minimal foreign language grammars sponsored by the Orthological Institute.” (The Orthological Institute was a creation of C. K. Ogden, the Basic English guy; I’m glad to see they sponsored more useful things as well.) Duff sounds like an interesting fellow (he seems to have appreciated Finnegans Wake when it was still Work in Progress); too bad there isn’t more available on him.