No. 15537. Argued November 3, 1960. Decided June 21, 1965. Miss Betty H. Olchin, of the bar of the Court of Appeals of New York, pro hac vice, by special leave of court, Cristobal, Canal Zone, with whom Messrs. Mozart G. Ratner and Isaac N. Groner, Washington, D.C., were on the brief for petitioners. Miss Margaret M. Farmer, Atty., N.L.R.B., with whom Messrs. Stuart Rothman, Gen. Counsel, N.L.R.B., at the time the brief was filed, Dominick L. Manoli, Associate Gen. Counsel, Marcel Mallet-Prevost