The eighth day of the week

Alfred Coppel, Alfredo Jose de Arana-Marini Coppel, was an American author. After serving as a fighter pilot during World War II, he started his career as a writer and became one of the most prolific pulp authors of the 1950s and 1960s. Though writing in a variety of genres, including action thrillers, he is known for his science fiction stories which comprise both short stories and novels. - Wikipedia