Imagine the company you work for has a policy that allows users to bring their personal computers to the office. How does this policy pose a threat to Layer 2 security? What additional policy/policies can help ensure an employees laptop does not infect the network?
For your citations, you might use articles that show examples of potential Layer 2 security risks with personal devices. You can also find articles from experts that suggest best practices for protecting networks that allow the use of personal devices.