In 1934, Mutual filed a complaint with the Federal Communications Commission (FCC) regarding its difficulties in establishing new stations, in a radio market that was already being saturated by NBC and CBS. In 1938, the FCC began a series of investigations into the practices of radio networks and published its report on the broadcasting of network radio programs in 1940. The report recommended that RCA give up control of either NBC Red or NBC Blue. At that time, the NBC Red Network was the principal radio network in the United States and, according to the FCC, RCA was using NBC Blue to eliminate any hint of competition. Having no power over the networks themselves, the FCC established a regulation forbidding licenses to be issued for radio stations if they were affiliated with a network which already owned multiple networks that provided content of public interest.