The Secretary is authorized to designate those auction markets where tobacco bought and sold thereon at auction, or the products customarily manufactured therefrom, moves in commerce. Before any market is designated by the Secretary under this section he shall determine by referendum the desire of tobacco growers who sold tobacco at auction on such market during the preceding marketing season. The Secretary may at his discretion hold one referendum for two or more markets or for all markets in a type area. No market or group of markets shall be designated by the Secretary unless two-thirds of the growers voting favor it. The Secretary shall have access to the tobacco records of the Collector of Internal Revenue and of the several collectors of internal revenue for the purpose of obtaining the names and addresses of growers who sold tobacco on any auction market, and the Secretary shall determine from said records t