Ethnologue is one of the most authoritative resource on world languages and is a required resource for your project
Ethnologue is published in 3 volumes, organized by region:
Within each volume, entries are organized by subregion and country (not by language or language family), so its important to have an idea of where your chosen language is spoken.
Language entries in Ethnologue always include the same components:
Here's an example:
If you need help, each volume has several indexes in the back to help you locate your specific language, including: