In the wake of accusations of plagiarism by Republican presidential hopeful Ben Carson in his bestseller America the Beautiful, Carson’s publisher, Zondervan, has issued a statement confirming the accusations, and Carson himself has apologized.

A story posted by BuzzFeed on January 6 brought the situation to light, asserting that a number of sections of Carson’s 2012 book "were plagiarized from various sources.” BuzzFeed noted that although Carson often cited the works he plagiarized in his end notes, he made "no effort to indicate that not just the source, but the words themselves, had been taken from different authors.”

The Buzzfeed article, which was picked up by various outlets, compared lengthy passages from America the Beautiful with material from books by other authors, as well as from a variety of news reports and several websites.

In response to the accusations, Zondervan released this statement on Thursday: “It has become apparent that further source citation is appropriate in Dr. Carson’s America the Beautiful. Any necessary updates will be made in subsequent printings.”

Additionally, Carson himself issued this apology: “I attempted to appropriately cite and acknowledge all sources in America the Beautiful, but inadvertently missed some. I apologize, and I am working with my editors to rectify the situation."

America the Beautiful sold modestly after its release in 2012, but got a big boost when Carson spoke at the National Prayer Breakfast in 2013. After a YouTube video of the speech went viral, the book sold 46,000 copies in six weeks, the New York Times reported. According to Nielsen BookScan, which tracks 80% of print sales, the trade paperback edition has sold, to date, about 284,000 copies.

BuzzFeed’s article compared its accusations against Carson to its 2013 story asserting that Kentucky Sen. Rand Paul had plagiarized passages of Government Bullies (Center Street/Hachette); BuzzFeed noted that Paul's book "was eventually updated to include attribution.”

Conservative historian William Federer, whose America’s God and Country is one of the books Carson allegedly plagiarized, has come to Carson's defense. In a letter sent to Carson, and released by Carson’s attorney and literary agent Sealy Yates, Federer wrote, "I was dismayed when I read a BuzzFeed article… and saw how the [Buzzfeed] author attempted to use my words in a subtly-crafted attack on Dr. Ben Carson's character by accusing him of plagiarism.”

Carson and Federer met while serving together on the board of Regent University, and in his letter Federer emphasized that he gave Carson permission to use any material he wanted. Federer wrote: “I feel grossly misrepresented in the BuzzFeed article. Errata is not plagiarism. Any missing attributions were simply editor's oversight.”

The BuzzFeed article also quoted Carson from America the Beautiful about being caught plagiarizing in college: “During my research for one of the papers in an advanced psychology course, I found some passages that seemed particularly appropriate, and I included them in my writing. I did not, however, indicate that this was the work of someone else; frankly, I had never even heard of the term plagiarism."

Update: At press time, Zondervan said it was unable to make any changes to the text in time for a forthcoming signature hardcover edition of America the Beautiful. Although it is listed on Amazon with an April publication date, Zondervan said it actually has a January 27 pub date and is shipping now. The company said citation updates will come in subsequent printings.