THOMAS WHITESIDE _was born in England in 1918 at Berwick-upon-Tweed, on the Scottish border. After working as a newspaperman in Canada, he came to this country in 1940. He is a United States citizen. After wartime service with the Office of War Information, he worked as a reporter for_ The New Republic, _and for some years he has been a writer for_ The New Yorker. _Mr. Whiteside is married to a French-born wife and has three children. They live in Greenwich Village. He is the author of_ The Relaxed Sell, _published in 1954_.