Gregory Kern is a pseudonym of E. C. Tubb.
Edwin Charles Tubb was a British writer of science fiction, fantasy and western novels. The author of over 140 novels and 230 short stories and novellas, using 58 pen names over five decades of writing, although some of these were publishers' house names also used by other writers. Tubb wrote 17 Cap Kennedy novels, all under the pseudonym Gregory Kern. - Wikipedia
Walter M. Miller Jr., Kurt Vonnegut, Ray Bradbury, Keith Laumer, Isaac Asimov, Philip Dick, Robert Silverberg, Frank Herbert, Ben Bova, Marion Zimmer Bradley, Frederik Pohl, Alfred Bester, Clifford D. Simak, Richard Matheson, H. Beam Piper, Annie Proulx, Poul Anderson, Hal Clement, Catherine Lucile Moore, Robert E. Howard, Robert Sheckley, Harry Harrison, Algis Budrys, Philip José Farmer, Frank M. Robinson, August Derleth, Fritz Leiber, James Blish, L. Ron Hubbard, Edgar Wallace, Manly Wade Wellman, Steve Rasnic Tem, C. M. Kornbluth, Dean Ing, Gordon R. Dickson, Terry Carr, Jerome Bixby, Edmond Hamilton, Jack Williamson, Clark Ashton Smith, William F. Nolan, Ron Goulart, Henry Kuttner, Lester del Rey, Andre Norton (duplicate), R. A. Lafferty, E. C. Tubb, Stanley G. Weinbaum, Karen Anderson, Judith Merril, Sydney J. Van Scyoc, William Tenn, Evelyn E. Smith, Tom Godwin, Laurence M. Janifer, Alan E. Nourse, Emil Petaja, Katherine MacLean, Edgar Pangborn, Helen M. Urban, Rhoda Broughton, Charles L. Fontenay, Milton Lesser, Melanie Tem, Sonya Dorman, Miriam Allen deFord, John D. MacDonald, Robert F. Young, Florence Verbell Brown, Dorothy Quick, Mary Elizabeth Counselman, Barbara Constant, Therese Windser, T. D. Hamm, Lilith Lorraine, Ann Warren Griffith, Frank W. Coggins, L. Taylor Hansen, Louis Trimble, Helen Huber, Mari Wolf, Anne Walker , Carl Jacobi, Lynn Venable, Mary Carlson, Ted White: One Hundred
by Walter M. Miller Jr., Kurt Vonnegut, Ray Bradbury, and 83 others