Martin Luther King Jr. borrowed words and ideas extensively from other sources for his doctoral dissertation and other writings without giving proper citations, a Stanford University historian says.

"Several of King's academic papers, as well as his dissertation, contain numerous appropriated passages that can be defined as plagiarism," historian Clayborne Carson said in a story The Wall Street Journal published Friday.The slain civil rights leader's wife, Coretta Scott King, chose Carson to lead The Martin Luther King Jr. Papers Project, which she founded in 1984 to gather his papers from locations around the country and produce a multivolume collection.

King's school papers are his most obscure and insignificant writings, but the discoveries have prompted debate, anguish and soul-searching among scholars who have worked on the project.

David Garrow, a member of the project's advisory board and author of "Bearing the Cross," a Pulitzer Prize-winning biography of King, said the discovery "had a tremendously shaking, emotional impact on me."

"To me, 98 percent of what makes it most interesting is: Why did he do it? Was he so insecure that he thought this was the only way to get by? It's disconcerting, because it is fundamentally, phenomenally out of character with my entire sense of the man."