NEW YORK (AP) — Dr. Ben Carson’s publisher will be revising future editions of his book “America the Beautiful” in response to allegations that the conservative activist failed to properly credit source material.

A BuzzFeed story earlier this week noted close similarities between passages in Carson’s 2012 book and material that first appeared elsewhere.

A spokeswoman for the publisher, Zondervan, issued a statement Thursday saying that “it has become apparent” that additional citations are needed.

Carson’s literary agent, Sealy Yates, told The Associated Press on Wednesday that Carson had submitted all of his sources to Zondervan before publication and thought that Zondervan would ensure there was attribution.

Carson, a former neurosurgeon, has been rumored as a possible Republican contender for the 2016 presidential election.

Zondervan is a Christian publisher owned by HarperCollins.