Answer:
telephone directory
Step-by-step explanation:
An atlas is a book that have a collection of maps.
A gazetteer is a geographical dictionary that has information like statistics, list of places, features of countries, regions.
A telephone directory is a book in which you can find contact information of people and businesses.
According to these definitions, if you were working on a geography project, the source that would probably be of least help to you is a telephone directory as it doesn't have any information related to geography.