Complex sentence: From 1987 to 1994, he was the editor of Saturday Night magazine where he pioneered the use of mixed circulation with inserted copies in The Globe and Mail and other newspapers in the old Southam Newspaper Group across Canada.
Split into simpler sentences: From 1987 to 1994, he was the editor of' Saturday Night. At Saturday Night, he pioneered the use of mixed circulation with inserted copies in The Globe and Mail and other newspapers in the old Southam Newspaper Group across Canada.