What is the principal type of supporting material used in the following? "if you owned a television in the late 1940s and very early 1950s, chances are that lots of friends dropped by to watch milton berle's the texaco star theater, sid caesar's your show of shows, the bob hope show, william bendix's the life of riley, as well as the comedy of jimmy durante, imogene coca, george burns, gracie allen, and jack benny."