At least 20 pages of Donald Trump Donald John TrumpUS reimposes UN sanctions on Iran amid increasing tensions Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Trump supporters chant 'Fill that seat' at North Carolina rally MORE's textbooks for real estate and wealth seminars were plagiarized from another book written 10 years earlier, according to The New York Times.

The Times compared an an excerpt from the Trump Institute's 2006 book, "Billionaire's Road Map to Success,” alongside the 1995 book, "Real Estate Mastery System: Mortgage and Finance,” and found a more than 100-word passage was lifted from the older book. The Democratic super-PAC American Bridge first noticed the similarity, according to the Times.

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At the time the 2006 book was published, Trump had appeared in an infomercial lauding the series and implying that its wealth and real estate tips came from or were endorsed by the businessman himself.

"I put all of my concepts that have worked so well for me, new and old, into our seminar. And people are loving it. People are really doing well in it and are loving it," he said in a clip of the infomercial available online.

Despite his endorsement, the program was owned by a couple who had been accused of fraud both by former customers as well as state regulators, the Times reported.

Alan Garten, Trump's counsel, told the paper he was unaware of the plagiarism charge and initially did not know of the fraud charges against the couple. While referring to the Institute as a "short-term licensing deal," Garten added, "I stand by the curriculum that was taught both at Trump University and Trump Institute."

It's the latest example of controversy involving Trump-branded products. He has faced significant criticism over his Trump University program, a real estate course that is accused of misleading students and is now battling fraud charges in federal court.

Unsealed internal program documents allege that staff members tried to convince students to go into debt or similarly overextend themselves in order to pay for the program, which cost up to $35,000.

When students balked at signing up, employees were told to emphasize Trump's endorsement, even though investigations and depositions found that Trump exercised little oversight over the program.