Complex sentence: He was the lead editor of "The New Republic" from 1997 to 1999--during which time Lane oversaw the work of Stephen Glass, a staff reporter who fabricated portions or all of 27 of 41 articles he wrote for the magazine.
Split into simpler sentences: He was the lead editor of "The New Republic" from 1997 to 1999. During his time as editor, Lane oversaw the work of Stephen Glass, a staff reporter who fabricated portions or all of 27 of 41 articles he wrote for the magazine.