The Conquerors appeared only in the magazine Science Wonder Stories and Fantastic Story Magazine.
David Henry Keller (1880–1966) was most often published as David H. Keller, MD, but also known by the pseudonyms Monk Smith, Matthew Smith, Amy Worth, Henry Cecil, Cecilia Henry, and Jacobus Hubelaire. He was a writer for pulp magazines in the mid-twentieth century who wrote science fiction, fantasy and horror. He was the first psychiatrist to write for the genre.
David H. Keller. Wikipedia.