The Stephen Ambrose saga continues.

Several more passages from the historian's current best seller, The Wild Blue, have been found to closely resemble the works of others, among them the autobiography of former Sen. George McGovern.

McGovern, whose experiences as a World War II bomber pilot are a featured part of the book, has defended Ambrose against allegations of plagiarism.

At least six books by Ambrose, including The Wild Blue and Undaunted Courage, have been questioned for failing to properly credit source material. The author recently posted an apology on his Web site, which includes a letter of support from McGovern.

On Wednesday, Forbes.com reported on several new additional passages in The Wild Blue. Here, for example, is a paragraph from Grassroots: The Autobiography of George McGovern, published in 1977:

"One day as we drove into his farmyard we saw Art sitting on the steps of his back porch, tears streaking down his dusty face. I had seldom seen an adult cry. Art Kendall explained to my dad that he had just received a check from the stockyards for a year's production of pigs. The check did not cover the cost of trucking the pigs to market."

Here's a passage from The Wild Blue, published last fall:

"Once, while hunting with his father, he saw a farmer named Art Kendall sitting on the steps of his back porch, tears streaming down his face. Kendall explained to McGovern's father that he had just received a check from the stockyards for that year's production of pigs. The check did not cover the cost of trucking the pigs to market."

McGovern, in a phone interview from his home near Missoula, Mont., told The Associated Press on Wednesday that "those last couple of sentences are very, very close but it doesn't cause me any pain. I really have no problem with it."

An Ambrose spokesman declined comment. Ambrose's publisher, Simon & Schuster, did not immediately return calls from The Associated Press.

The historian has blamed the errors on his recent prolific pace  Ambrose has averaged more than a book a year since the mid-1990s  but two books from the 1970s also have been cited.

Ambrose, who said recently he would write just one more book and then devote his time to conservation issues, has sounded both contrite and unconcerned in previous remarks. He apologized after the first allegation emerged, that The Wild Blue contained several passages close to Thomas Childers' Wings of Morning.

But he has also defended his work, saying: "If I am writing up a passage and it is a story I want to tell and this story fits and a part of it is from other people's writing, I just type it up that way and put in a footnote. I just want to know where ... it came from."

Historians traditionally consider footnotes inadequate credit for material highly similar to its source.