. "A telephone directory, also known as a telephone book, telephone address book, phone book, or the white/yellow pages, is a listing of telephone subscribers in a geographical area or subscribers to services provided by the organization that publishes the directory. Its purpose is to allow the telephone number of a subscriber identified by name and address to be found.The advent of the Internet and smart phones in the 21st century greatly reduced the need for a paper phone book."@en . .