The first two are the authors of the only books first published in the 19th century that Collins published. Artist on Twain's work is Margaret Paull.
The next two are Canadians. Ralph Allen edited A Maclean's Reader, a collection of articles from Maclean's magazine. The artist is Franklin Arbuckle. Thomas P. Kelley was the Zelig of Canadian paperback authors - turning up everywhere including his one book for White Circle, Famous Canadian Crimes - articles originally published in New Liberty magazine. More on Mr. Kelley later.
Finally, an American, Joseph Mitchell, with McSorley's Wonderful Saloon. An edition was published a few years ago and is readily available. The artist is York Wilson.