Complex sentence: Instead of replacing him with another editor, Popular assigned editor-in-chief Alden H. Norton to add the magazines to his responsibilities; this arrangement lasted for seven months, after which Norton asked Pohl to return as his assistant.
Split into simpler sentences: Instead of replacing Pohl, Popular assigned editor-in-chief Alden H. Norton to add the magazines to his responsibilities. The arrangement lasted for seven months, after which Norton asked Pohl to return as his assistant.