No. 97-1454, No. 97-1660 Argued September 1, 1998 Decided September 29, 1998 On Petitions for Review and Cross-Applications for Enforcement of Orders of the National Labor Relations Board. Minh N. Vu argued the cause for the petitioners. Maureen E. Mahoney and Gregg J. Tucek were on brief. Julie B. Broido, Attorney, National Labor Relations Board, argued the cause for the respondent. Linda Sher, Associate General Counsel, John D. Burgoyne, Acting Deputy Associate General Counsel, and Peter D. Winkler