"With reference to" is also acceptable, but it's less common and often sounds more formal.
Here's a breakdown:
* In reference to: This phrase means "regarding" or "concerning." It's used to introduce a topic or subject that you're about to discuss.
* Example: "In reference to your email, I have attached the document you requested."
* With reference to: This phrase is similar to "in reference to," but it's often used in more formal contexts, such as business correspondence.
* Example: "With reference to our previous conversation, I would like to update you on the status of the project."
Ultimately, both phrases are correct, but "in reference to" is more commonly used.