Two Pulitzer Prize-winning scholars are asserting that the collection of the Reverend Martin Luther King Jr.’s papers, going on exhibit tomorrow at Sotheby’s and being auctioned on June 30, is not worth any research institution’s investment of between $15 million and $30 million, given the conditions of the sale, under which the King estate retains copyright control. These constraints have undermined previous attempts to sell the collection.

At the same time, Mayor Bloomberg’s recent comments in Atlanta leave open the possibility that either institutions or individuals in New York or perhaps the city itself might be interested in acquiring the collection. Speaking in Atlanta at a press conference with Atlanta Mayor Shirley Franklin last week, Mr. Bloomberg responded coyly to Ms. Franklin’s mention of New York’s interest in the papers.

“We are certainly exploring the possibility, but we know New York is exploring the possibility, we think they are,” Ms. Franklin said. “So: Mum is the word.”

When a reporter prompted Mr. Bloomberg to comment, his reply was equally cryptic. “I thought the mayor said it very well: ‘Mum is the word,'” he said. “But, what is true, clearly, is that this is a very important collection from a scholarly point of view. It is a collection that spans King’s whole life and has some documents that really have great historical significance. Historians and librarians are interested in this collection.”

Yet some scholars are skeptical of the value of the collection as it is now being offered. Taylor Branch, the author of a three-volume biography of King, said a library asked him “if I’d be willing to try to make a public appeal for angels to donate the money, and I said I couldn’t do it in good conscience until the conditions are clear.”

“My qualm is not the amount of money involved,” Mr. Branch said. “I would in good conscience ask for some wealthy person to buy and donate the materials, but not if they’re then going to turn around find a bunch of lawyers on the step of the donated institution talking about all these conditions of sale that will limit access.”

Mr. Branch’s concern stems from the King estate’s longtime practice of attempting to limit what researchers can quote from King’s writings and speeches. Mr. Branch said that when he was working on the second volume of his biography, “Pillar of Fire,” he received a letter from a lawyer for the estate claiming that he needed a license to write his book-“more or less as though I were going to make a Martin Luther King belt buckle.” Mr. Branch said he ignored the letter.

David Garrow, the author of “Bearing the Cross: Martin Luther King Jr. and the Southern Christian Leadership Conference,” also said that he didn’t think a university could justify spending the money on the collection, with the King family retaining copyright. “You’re not buying anything but a succession of an endless headaches, if you acquire these, allow scholars to look at them, but no one can actually publish anything and quote from them,” Mr. Garrow said. “All you do is put yourself in a position of being a kind of intermediary for life between scholars and this greedy estate.”

A spokesman for the King Center in Atlanta, representing the King family, did not respond to a request for comments.

The issue of copyright control contributed to the failure of negotiations, in the summer of 2003, between the King estate and the Center for American History at the University of Texas at Austin. Sotheby’s was at that time offering the collection, which it had appraised at $30 million, for private sale on behalf of the estate. The Center’s director, Don E. Carleton, looked at the exhibit in New York and flew to Atlanta to look at the part of the material that was in Mrs. King’s house. But a combination of the price and the copyright issue made him decide against buying it. An attempt by the Library of Congress to reach a deal in 1999 also foundered on the issues of price and copyright control.

“If you buy a collection and spend that kind of money, you want to be pretty free to open it up for scholarship and have things published,” Mr. Carleton said. In most cases, he said, copyright doesn’t inhibit what use researchers can make of material. “But the history of the King estate’s handling of the King literary rights has been rather troubling. You have to make a decision if you’re going to acquire the collection: Do you really want to enter into a partnership with people who have proven themselves in the past to be extremely difficult?”

Another factor that made him decide against purchasing the collection, Mr. Carleton said, was that much of the material was preserved elsewhere, and the material of most interest to scholars – a collection of nearly 100 sermons by King – was to be published as part of the King Papers by the Martin Luther King Jr. Institute of Education and Research at Stanford. “One of the reasons we would spend a lot of money on something is if we thought that we were saving the intellectual content of it from destruction or dispersal.” In this case, since the sermons were to be published as a volume of the King Papers Project (which will come out next year), he couldn’t justify the price.

Several individuals and institutions have been reported to be considering purchasing the collection. According to the Atlanta Journal Constitution, a consortium of individuals in Atlanta, including a construction magnate, Herman Russell, and a former aide to King and Ambassador to the United Nations, Andrew Young, is trying to put together the money to keep the collection in Atlanta, possibly at Emory University. A spokesman for the Smithsonian Institution said that the Smithsonian is “very interested” in acquiring the papers for its new National Museum of African American History and Culture.

It wasn’t clear from Mayor Bloomberg’s remarks in Atlanta whether he was implying that the city itself was interested in bidding on the collection or whether institutions within the city were trying to raise money for the purchase. The Mayor’s office declined to elaborate on his comments.

The New York Public Library is said to be looking at the collection, but also to be concerned about the copyright issue. A Library spokesman declined to comment.

Although the King estate retains copyright, if a qualified institution purchases the collection, the estate will grant the institution what Sotheby’s Vice President David Redden called “expanded fair use rights.” This would allow the institution to use excerpts or images of the material-up to 10% of any given document-on its Web site or in press materials.

Sotheby’s has sent a document elaborating the “conditions of sale” to interested institutions. It enumerates an institution’s fair use rights, but there is one clause that seems to contradict the rest of the conditions -“Your rights granted here under shall not extend to publication or other use of the text of any of Dr. King’s copyrighted speeches, sermons, books or other writings, in whole or in part.”

It is not uncommon for literary estates to maintain intellectual property rights after donating their materials to archives, but Mr. Branch questioned the motivations of the King estate in this case, when they are also asking for such a large sum of money. “Why do they want to maintain copyright control if they’re getting $15 million?” he said. “There could be a lot of mischief in that. I’ve had libraries say, ‘This scares us off.’ Everybody’s heard nightmare situations about what copyright control can be asserted to mean by the estate. Nobody wants to get into a situation where they pay $15 million, and then next thing they know the whole thing is closed because they’re in a fight with the King family about whether they control who gets in to do research.”

According to Mr. Branch, Mr. Redden has told interested institutions that the conditions of sale are a “work in progress.” In an interview, Mr. Redden said, “Well, I’m still tailoring them, tweaking them to a small extent. I want to make them as useful as they possibly can be to the institutions.”