HDTV technology was introduced in the United States in the late 1980s and made official in 1993 by the Digital HDTV Grand Alliance, a group of television, electronic equipment, communications companies consisting of AT&T Bell Labs, General Instrument, Philips, Sarnoff, Thomson, Zenith and the Massachusetts Institute of Technology. AT&T, Philips, Zenith, and MIT, among others, made up what group in the 90's?