No. 23984. Argued October 23, 1970. Decided January 8, 1971. Reargued April 23, 1971. Decided June 25, 1971. Mr. Joel D. Blackmon, Washington, D.C., for petitioners. Miss Vivien Asplund, Atty., National Labor Relations Board of the bar of the Court of Appeals of New York, pro hac vice, by special leave of Court, with whom Messrs. Arnold Ordman, Gen. Counsel, Dominick L. Manoli, Associate Gen. Counsel, Marcel Mallet-Prevost, Asst. Gen. Counsel, and Glen M. Bendixsen, Atty., National Labor Relations