Nos. 18921, 20211. Argued November 22, 1966. Decided March 24, 1967. Petitions for Rehearing Denied April 21, 1967. Mr. Michael Gottesman, Washington, D.C., with whom Mr. Elliott Bredhoff, Washington, D.C., was on the brief, for petitioner in No. 18,921 and intervenor in No. 20,211. Mrs. Janet Kohn, Atty., N.L.R.B., with whom Messrs. Arnold Ordman, Gen. Counsel, Dominick L. Manoli, Associate Gen. Counsel, Marcel Mallet-Prevost, Asst. Gen. Counsel, and Warren M. Davison, Atty., N.L.R.B., were on the