Three members of the Berkshire Museum said they would continue to fight the sale of 40 works, including the Norman Rockwell painting Shuffleton’s Barbershop, considered to be core holdings of the Massachusetts museum. The institution has argued it needs to liquidate works in order to expand its endowment, revamp the museum, and balance precarious finances. “The petition to which the Attorney General’s office has agreed claims to have convinced it that the museum’s financial condition is indeed perilous, yet the office chose not to require any change in the governance or management of the institution by the board that will now be entrusted with a $50 million windfall,” Nicholas M. O’Donnell, a partner at Sullivan & Worcester LLP, said in a statement on behalf of his clients, who had sued last fall to halt the sale. Earlier in February, the Massachusetts Attorney General and the Berkshire Museum said they had come to an agreement that would allow the museum to sell its prized Rockwell to an as yet unnamed nonprofit museum. The New York Times reported that, under the agreement, the painting will go first to the Norman Rockwell Museum in Stockbridge, Massachusetts for 18 to 24 months after which it may be displayed in other museums in the state or loaned nationally or internationally. Members of the Rockwell family, who had joined separate litigation against the sale, announced on Friday that they would cease their opposition as a result of the settlement.