Trustees all over the country have been receiving a book critical of Islam, with no cover note, leading some to worry about why they were receiving the packages.

The address on the packages referred to their trustee status.

The book is Islamic Imperialism: A History, published by Yale University Press. The author is Efraim Karsh, a professor at the University of London who is highly regarded in neoconservative circles, but who has been harshly criticized by many in Middle Eastern studies. According to the Yale press, the book argues that the attacks on 9/11 reflect Islamic imperialism, and "Islam's war for world mastery."

The Association of Governing Boards of Colleges and Universities sent an alert to members Wednesday disavowing any connection to the mailing, and saying that it would not have given out trustees' names so that someone could mail them the books. The AGB alert said that law enforcement officials were looking into the mailings.

The books were sent by the Ethics and Public Policy Center, a Washington-based think tank that says it was founded "to clarify and reinforce the bond between the Judeo-Christian moral tradition and the public debate over domestic and foreign policy issues."

M. Edward Whelan III, president of the center, confirmed Wednesday that his group had sent the books, and said that he did not know how many trustees were receiving them. The AGB  alert said that 50,000 books had been shipped. Whelan said that trustees were not the only recipients and that some of the books had been sent to journalists and lawmakers, among others.

"We sent it to a broad range of folks in positions of responsibility," he said, "to prod thinking" about the challenges "posed by radical Islam." Whelan called the book "important, provocative, interesting."

Asked why there was no cover note explaining who was sending the book and why, he said that he believed the book "should speak for itself." As for trustees being concerned about receiving a book with no explanation, he said that "if trustees are disturbed by receiving this book, I think that signals a bigger problem in higher education."