Nos. 73-1489, 73-1579 and 73-1605. Argued April 5, 1974. Decided June 21, 1974. David Nevins, Washington, D.C., of the bar of the Supreme Court of Minnesota, pro hac vice, by special leave of court, for petitioners. Barry S. Jellison and David J. Salniker were on the brief for petitioners. Robert A. Giannasi, Atty., NLRB, with whom John S. Irving, Deputy Gen. Counsel, Patrick Hardin, Associate Gen. Counsel, and Elliott Moore, Deputy Associate Gen. Counsel, NLRB, were on the brief, for respondent