Goodwin said problems in checking citations, including misplacing an important book, was the primary reason for the lack of citations.

She had previously cited taking notes longhand as the reason for the misattributions, but on Saturday said her next book was also done in longhand, and that the problems with her scholarship were of a different sort.

For example, neither Goodwin nor her research assistants sought a new copy of Kathleen Kennedy: Her Life and Times, the book she had misplaced and the book from which the original discovery of misattributed passages stemmed.

Lynne McTaggart, author of the book on Kathleen Kennedy, discovered extensive copying in Goodwin’s book and received a cash settlement and a confidentiality agreement after bringing the plagiarism to the attention of Goodwin’s publisher.

In the revised version, Goodwin added more footnotes, bringing the total to over 3,500, and cited McTaggart in the preface to her book.

Harvard has continued to support Goodwin.

“Doris Kearns Goodwin has served with distinction on the Board of Overseers,” wrote University spokesperson Rebecca Rollins in an e-mail. “In recent weeks, she has spoken directly to questions raised about her books, and her comments speak for themselves.”

Goodwin did not return repeated calls for comment.

—Staff writer Andrew J. Miller can be reached at amiller@fas.harvard.edu.