No. 75-1085. Argued September 8, 1975. Decided December 18, 1975. John P. Flynn, Braintree, Mass., with whom Murphy, Lamere Murphy, Braintree, Mass., was on brief, for petitioners. Allison W. Brown, Jr., Washington, D.C., Atty., with whom John C. Miller, Acting Gen. Counsel, John S. Irving, Deputy Gen. Counsel, Elliott Moore, Deputy Associate Gen. Counsel, Alan D. Cirker and Sandra Shands Elligers, Washington, D.C., Attys., were on brief, for respondent N.L.R.B. Alan J. McDonald, Boston, Mass., with