A passage regarding plagiarism in “Sources: Their Use and Acknowledgement,” a handbook created by Dartmouth College and distributed to Yalies — with permission — states that “any direct quotation must be placed in quotation marks, and the source immediately cited.”

But best-selling historian Stephen Ambrose seems never to have read these guidelines.

In several passages of his current best-seller about B-24 pilots in World War II, “The Wild Blue,” Ambrose directly copied passages from other authors’ works without properly attributing the passages to them. The authors and their works are footnoted as sources, but the passages are not in quotation marks.

Several passages from “The Wild Blue” are direct quotes from Thomas Childers’ historical account, “Wings of Morning.” For example, both books describe B-24 bombers as “popping up out of the clouds” and “glittering like mica.” Childers, a professor at the University of Pennsylvania, recently announced that he will no longer use Ambrose’s books in his courses.

Childers said he is surprised at the attention the story has gotten since it broke.

“It’s very odd,” Childers said. “It’s been crazy around here with television stations calling.”

Childers said that, ironically, he has benefitted from the controversy.

“‘Wings of Morning’ came out in 1995,” Childers said. “It was successful, [but now] sales have gone up.”

The New York Times reported that Ambrose also lifted passages from other authors in “The Wild Blue.”

Ambrose has apologized, releasing a statement that said he used “The Wings of Morning” for three passages of his novel, and that he cited Childers and his book in the footnotes.

“But I failed to put some words and sentences of Dr. Childer’s [sic] into quotation marks,” Ambrose said in a statement quoted on Forbes.com. “I am sorry for this omission and apologize to him. I will make that change, putting his words into quotation marks, in all future editions of my book.”

Ambrose has written more than 30 books, at least two of which — “The Wild Blue,” and “Crazy Horse and Custer” — have been called into question for Ambrose’s failure to attribute words properly to their authors.

Yale History Department chairman Jon Butler said he believes Ambrose stopped being a critical historian long ago.

“This is one of the reasons he falls into the trap of so easily ‘borrowing’ other peoples’ work without even realizing that he’s doing it,” Butler said. “In short, he really is a popular writer and not a historian.”

Though Ambrose has been widely criticized for his misrepresentation, he continues to sell books. In a Jan. 11 article for Forbes.com, Mark Lewis wrote, “[Ambrose’s] next book — inevitably will be another bestseller.”

Paul Miserendino, book department manager at the Yale Bookstore, said he believes that Ambrose’s book sales will thrive despite the controversy.

“I really don’t think [the controversy] will have any effect on the sales of Stephen Ambrose,” Miserendino said. “He’s a well-known historian and author; he sells many copies of the books he puts out.”

Miserendino cited another example of an author’s success despite controversy regarding his integrity. The Pulitzer Prize-winning book “Founding Brothers: The Revolutionary Generation,” by Joseph Ellis, is still a best seller, Miserendino said, despite Ellis’ suspension from teaching at Mount Holyoke College after misrepresenting his past.

Ellis told students he had served in Vietnam, when in fact he did not.