![Pacific Bell Yellow Pages](https://cdn.statically.io/img/static.wikia.nocookie.net/memoryalpha/images/8/80/Pacific_Bell_Yellow_Pages.jpg/revision/latest/scale-to-width-down/180?cb=20120730071711&path-prefix=en)
The Yellow Pages advertisement
![Pacific Bell payphone](https://cdn.statically.io/img/static.wikia.nocookie.net/memoryalpha/images/4/46/Pacific_Bell_payphone.jpg/revision/latest/scale-to-width-down/180?cb=20200111142915&path-prefix=en)
The Yellow Pages in a San Francisco payphone booth
The Yellow Pages were 20th century telephone directories that listed where certain businesses were located and what their phone numbers were.
Sulu, Scotty, and McCoy saw an advertisement for the Pacific Bell Yellow Pages when they were trying to figure out how to make a whale tank while visiting San Francisco in 1986.
Pavel Chekov and Uhura also consulted the Yellow Pages in a telephone booth to assist them in locating the US Navy base in Alameda. (Star Trek IV: The Voyage Home)