29 C.F.R. § 1203.2
Applications for the services of the National Mediation Board under section 2, Ninth, of the Railway Labor Act to investigate representation disputes among carriers' employees may be made on printed forms NMB-3, copies of which may be secured from the Board's Representation and Legal Department or on the internet at www.nmb.gov. Such applications and all correspondence connected therewith should be filed in duplicate and the applications should be accompanied by signed authorization cards from the employees composing the craft or class involved in the dispute. The applications should show specifically the name or description of the craft or class of employees involved, the name of the invoking organization or employee seeking certification, or the name of the employee seeking decertification, the name of the organization currently representing the employees, if any, and the estimated number of employees in each craft or class involved. The applications should be signed by the chief executive of the invoking organization, some other authorized officer of the organization, or by the invoking employee. These disputes are given docket numbers in the series "R".
29 C.F.R. §1203.2