Section 7B(3)(a) in The Bengal Industrial Employment (Standing Orders) Rules, 1946
(a)where the appeal is filed by the employer or a workman, to the trade union or unions of the workmen named by the employer or the workman or to any other trade union or unions which may be known to such appellate authority as concerned with the establishment or establishments to which the Standing Orders relate, and where there is or are no such trade union or unions, to the workmen of such establishment or establishments by affixing it on the notice board at the office of the appellate authority and of the establishment or establishments concerned ;