An academic researcher has found 11 passages in Senator Kerry’s published writings that appear to have been taken from other works without attribution, though experts disagree about whether the copying should be considered plagiarism.

Six of the passages come from Mr. Kerry’s 1997 book, “The New War: The Web of Crime That Threatens America’s National Security.” All bear some similarity to news accounts that preceded publication of the book.

In one instance, Mr. Kerry wrote, “Russian mobsters have been arrested in Germany for extortion, car theft, counterfeiting, prostitution, selling drugs and illegal weapons, and smuggling everything from icons to uranium.”

A 1993 Philadelphia Inquirer article, written by Barbara Demick, said, “Suspected Russian mobsters have been arrested in Germany and charged with extortion, car thefts, counterfeiting, prostitution, gambling, and selling drugs and illegal weapons. They have been caught smuggling everything from religious icons to uranium.” Mr. Kerry’s book contains endnotes but makes no reference to the Inquirer story.

A former English professor and author of two books on plagiarism, Robert Harris, examined that example and others and concluded that many of the instances clearly constituted plagiarism.

“If I had that in a student paper, I’d fail the paper, give them a zero, and make them redo it. On a second offense, I’d fail them for the course,” he said. “This kind of plagiarizing, it’s really unprofessional.”

Another plagiarism expert, Thomas Mallon, said he does not discuss individual cases but would be inclined to apply a more lax standard to Mr. Kerry than is typically used in academia.

“If you want to live in the real world, a politician has to be cut a bit of slack,” said Mr. Mallon, who wrote an oft-cited book on plagiarism, “Stolen Words.” He said one reason to be more lenient is that everyone assumes that most words uttered by politicians or published under their names were actually written by speechwriters or ghostwriters. “Realism dictates that any reader who spots unattributed passages has to concede a certain exculpation to the politician simply on the assumption that the politician did not write the material,” Mr. Mallon said.

Mr. Harris took a different view. “If we’re trying to fight plagiarism in the schools and kids see politicians doing it or getting away with it, that makes the battle all the much harder,” he said.

Both Messrs. Mallon and Harris said they are supporters of President Bush. They also said they did not believe that fact had colored their assessment of the situation.

A spokesman for Mr. Kerry’s campaign did not respond to phone and email messages seeking comment for this story. Told of the allegations, a former counsel to the senator, Jonathan Winer, said he was “highly suspicious” that they were surfacing so close to the election.

In another passage in “The New War,” Mr. Kerry wrote, “Recent reports indicate that uranium is being stored in the sort of lockers used by students in American high schools. In Murmansk, a Russian naval officer crawled though a hole in the fence surrounding a submarine fuel facility, broke into a locker, and hacked off a ten-pound hunk of enriched uranium, which he hid in his garage. He was caught only when he attempted to find a buyer.”

An article that appeared in Maclean’s magazine in April 1996, written by Malcolm Gray and William Lowther, reads,”Uranium is kept in the sort of lockers found in North American high schools….A Russian naval officer in Murmansk who crawled through a hole in the fence surrounding a submarine fuel facility…entered a building that was unlocked, broke into a locker, hacked off a 10-lb. chunk of enriched uranium and hid it in his garage. He was looking for a buyer when he was caught.”

The Maclean’s article is cited in Mr. Kerry’s book but only as the source of a direct quote that appears earlier.

In “Our Plan for America: Stronger at Home and Respected in the World,” the official campaign book for Mr. Kerry and his running mate, Senator Edwards of North Carolina, the candidates write at one juncture about the benefits of wind power as an energy source. “In many states, individual farmers and ranchers lease their property to wind power companies and receive an annual payment for having wind turbines on their property. With the right leadership, this could become a ‘cash crop’ for many other farmers and ranchers from around the country and stabilize rural economies,” they wrote.

An Energy Department fact sheet published in January 2003 reads, “In many states, individual farmers and ranchers lease their property to wind power companies and receive an annual payment for having one or more wind turbines on their property. This could become a predictable ‘cash crop’ for many other farmers and ranchers across the country, and help to boost farm and ranching incomes and stabilize rural economies.”

The examples of alleged plagiarism were compiled by a doctoral candidate who asked not be further identified. He declined to discuss his political views, but insisted that he is not connected with President Bush’s campaign. “I don’t normally, even in private discussions, get involved in politics,” he said. “I don’t hate Kerry.”

The student said he picked up a copy of “The New War” early last year and became suspicious that some sections of it might not have been properly attributed. He soon began looking at other of Mr. Kerry’s writings. “This just struck me as interesting,” the student said. He said his interest was fueled further by a recent spate of stories about plagiarism allegedly committed by high-profile figures, such as a Harvard law professor Laurence Tribe and two popular historians, Stephen Ambrose and Doris Kearns Goodwin.

The New York Sun first reported earlier this month on one of the cases the researcher identified, a passage in a Kerry speech about desegregation that appeared to have come from an article in an online magazine, Slate.

The student said he did not step forward sooner because he was concerned that he might be harassed if his identity were exposed. He recently attempted, unsuccessfully, to sell his research through an Indianapolis lawyer. The Sun, which first obtained details of the charges on Friday, did not provide the source with any compensation.

In a statement, a spokeswoman for Simon & Schuster, which published “The New War,” said the publishing house “stands behind Senator Kerry’s book.” She declined further comment.

However, one outlet for the senator’s work, a well-known journal, Foreign Policy, disputed one claim of missing attribution.

In an article the journal published in March 2003, Mr. Kerry wrote, “As of January 2002, the U.S. Army had an average 44 percent shortfall in translators and interpreters in five critical languages: Arabic, Korean, Mandarin-Chinese, Persian-Farsi and Russian. The State Department reported a 26 percent shortage of authorized translators and interpreters.”

About a year earlier, a similar passage appeared in the magazine Government Executive. In that article, Katherine Peters wrote, “The Army reported on average, a 44 percent shortfall in translators and interpreters in five critical languages-Arabic, Korean, Mandarin-Chinese, Persian-Farsi and Russian. The State Department has a 26 percent shortfall in authorized translator and interpreter positions.”

A spokesman for Foreign Policy, Jeffrey Marn, said Mr. Kerry’s article was not based on the earlier story by Ms. Peters.

“The sole source was a January 2002 report to Congress by the Government Accounting Office, ‘Foreign Languages: Human Capital Approach Needed to Correct Staffing and Proficiency Shortfalls,'” Mr. Marn wrote in response to a query from the Sun. “The information cited from the GAO report was an official statistic from a public record. The sentence is neither inaccurate nor is it plagiarized.”

The year-old article, which as of yesterday was prominently featured on Foreign Policy’s home page on the Web, does not make reference to the report prepared for Congress or to the Government Executive piece.

Mr. Kerry’s article also appears to misstate somewhat the accounting office’s findings. The report prepared for Congress found that the State Department had not filled 13 of its 50 authorized, budgeted positions for linguists. However, it also noted that State had “more than 1,800 translators and interpreters who could be called upon as needed” for contract work.

Oddly, one of Mr. Kerry’s closest advisers in his current campaign for the White House, John Sasso, played a key role in exposing one of America’s most renowned cases of political plagiarism. In 1987, Senator Biden withdrew from the Democratic presidential primary after it was disclosed that large portions of his closing statement at a debate were nearly identical to portions of speeches delivered earlier by a leader of Britain’s Labour Party.

At the time Mr. Sasso was manager of the campaign of one of Mr. Biden’s rivals, a governor of Massachusetts, Michael Dukakis. Mr. Sasso gave several reporters a videotape highlighting the similar speeches. At first he denied involvement in bringing the plagiarism to light, but later he admitted to it. Mr. Dukakis fired Mr. Sasso, but rehired him after winning the nomination.