General:
* Mention
* Refer to
* Quote
* Allude to
* Point out
* Name
* Identify
* Indicate
* State
* List
Formal/Academic:
* Reference
* Acknowledge
* Document
* Source
* Attribute
Informal:
* Bring up
* Call out
* Use as an example
The best synonym will depend on the specific situation. For example, "quote" is a good synonym if you are referring to the exact words of a source. "Mention" is more general and can be used to refer to simply bringing something up.