A book that has fueled corruption allegations at the center of an unfolding impeachment inquiry against President Donald Trump appears to have lifted portions of text from news articles and Wikipedia pages without proper citation or attribution.

The Daily Beast found more than a dozen instances in which Secret Empires, the bestselling book by investigative journalist Peter Schweizer, copied nearly complete sentences or sizable portions of them verbatim or near-verbatim from other sources. In a number of instances, those sources were uncited Wikipedia pages created before the book’s publication in early 2018.

Many of the passages included citations of the works from which language was drawn, but did not put that language in quotation marks. In one case, Schweizer’s book used language nearly identical to a post on a website of a prominent progressive think tank, but cited not that think tank, but a news article based on the same data.

The Daily Beast presented Schweizer’s spokesperson and his publisher, HarperCollins, with a detailed spreadsheet comparing the book’s text with that of the sources from which he appeared to have lifted language. That spokesperson, Sandy Schulz, denied that the examples constituted any sort of journalistic or academic misconduct.

“This is not plagiarism,” she said in an emailed statement. “Secret Empires was run through Grammarly’s plagiarism checker years ago. The examples you cite are trivial snatches of words occurring in a straightforward recitation of publicly available facts... If the analysis you apply to these selected passages were to become the standard, research-driven journalism, including yours, would become near-impossible.”

Schweizer’s book unearthed extensive details of allegedly corrupt schemes involving, among others, Hunter Biden, the youngest son of Democratic presidential candidate and former Vice President Joe Biden. Schweizer's reporting has informed allegations by others, chiefly President Donald Trump, that the elder Biden helped unseat a Ukrainian prosecutor to protect a company whose board included Biden’s son from investigation. That allegation has been largely debunked. But controversy spawned in large measure by Schweizer's reporting is nevertheless central to a rapidly escalating scandal that threatens to envelop the Trump administration.

None of the passages examined by The Daily Beast came from the section of the book that deals with the Bidens. The most problematic portion of Secret Empires appears to be a chapter focused on former Chicago Mayor Richard Daley. That chapter contains four passages that are largely copied from the Wikipedia page for Daley’s son Patrick. The book’s footnotes cite news stories that are cited in the same Wikipedia page, but the language appears to be lifted from the latter.

Three other passages in the book also appear to draw on Wikipedia pages, though with smaller sections of the sentences at issue, and in less specific language.

Other sections of the book more directly cite the sources from which language appears to have been lifted. But those sections nonetheless copy large portions of text from those sources and do not place quotation marks around them.

A section on the family of Illinois Gov. J.B. Pritzker, for instance, draws from and cites a Chicago Tribune article about a federal clean-energy grant to a Chicago-based company with ties to the Pritzker clan. But significant portions of the passage mirror, word-for-word, language in the Tribune piece, and do not appear in quotation marks.

The Daily Beast found five other instances in which Schweizer uses similar or identical language to sources that are cited in the text, but without denoting any direct quotation.

In one instance, Schweizer appears to have lifted language from a piece on the website of the Center for American Progress, a prominent progressive think tank, regarding Trump’s business activities abroad. The book cites not that piece but a Washington Post story on the underlying data. But Schweizer’s language mirrors not the Post’s, but CAP’s, down to the names of the same four countries, out of 18, in which Trump did business and the order in which they’re mentioned.

Columbia University defines “intentional” plagiarism to include a “direct copy [and] paste” of source text or a “small modification by word switch.” Its definition of “unintentional” plagiarism includes a “failure to ‘quote’ or block quote author's exact words, even if documented” and a “failure to put a paraphrase in your own words, even if documented.”

Hard-and-fast definitions of plagiarism are nonetheless disputed, especially in the digital age. “Both journalism and plagiarism have fallen into a murky new reality in which there’s no clear consensus about the old rules. Even the authorities who make the rules disagree over basic definitions,” wrote Washington Post senior editor Marc Fisher in a 2015 column in the Columbia Journalism Review. “The same technology that has softened the definition of plagiarism has also made it radically easier to plagiarize, intentionally or not.”

According to the acknowledgements in Secret Empires, Schweizer, who leads the nonprofit Government Accountability Institute, received assistance for the book from eight researchers and two interns.

It’s not his first work to upend American politics heading into a presidential election. His previous book, the bestseller Clinton Cash, detailed extensive conflict-of-interest allegations against then-Democratic presidential candidate Hillary Clinton. Scrutiny of her family’s charitable foundation dogged Clinton’s candidacy until her eventual defeat.

The investigative work in Secret Empires is sure to have a similar effect if Biden wins the Democratic nomination and challenges Trump next year. But already it’s fueling a national scandal that has congressional Democrats eyeing impeachment proceedings against the president.

The book’s allegations against the Bidens were front and center in Trump’s mind during a now-infamous July phone call with the new president of Ukraine, whom Trump asked to rekindle an official investigation into the elder Biden’s efforts to get the former prosecutor in Kyiv fired.

Trump has also credited Schweizer’s work publicly, quoting and name-checking him in a recent tweet that went after Biden.

All the attention has made Schweizer’s book a bestseller once again, as noted by Breitbart News, where he serves as a senior contributor. “Schweizer’s ‘Secret Empires’ Rockets to #17 on Amazon 1.5 Years After Release,” declared a headline Sunday.

An earlier version of this story gave the impression Schweizer had alleged a role by former vice president Joe Biden in the firing of a Ukrainian prosecutor. Schweizer has not made that allegation.