How To Write A Professional Reference For Coworker Example . It’s always written in a positive way. Anthony's abilities as a software engineer and leader. Professional Letter For Coworker • Invitation Template Ideas from howtostepmom.com As a supervisor, a recommendation letter written by you holds a lot of weight. I have worked with candidate x for the past x years. This recommendation letter sample is one written by a coworker for someone applying outside of the company.