Pacific Bell
From Memory Alpha, the free Star Trek reference
Pacific Bell was a telephone company operating in California, Earth in the late 20th century.
In 1986, the company published a register called Yellow Pages, which listed all businesses in a certain area. An advertisement for this was seen by Scotty, Sulu, and McCoy in San Francisco. They then used the Yellow Pages to search for a firm which could produce transparent aluminum and found Plexicorp. (Star Trek IV: The Voyage Home)
