Work references are not nearly as important as personal. Besides, in most places a work reference isn't permitted by law anyway to detail or comment on your performance other than to confirm your employment. Thus, it is the personal references that count.

Ensure however these are not purely social acquaintances. They should be people who are professionals who can speak to your character. Yep, professors are good. But surely you have peers who are professional? On my resume, I have included: a work colleague, a person I managed, and a person I encountered during my usual workday (sometimes this has been a client or customer of mine).

Make sure however that your references are constantly tweaked in that they remain current and relevant. A professor is a great idea - providing they taught you within the last year (two at most). Also, ensure you have the individual's permission to use as a reference. I continue to get calls for a reference for a former colleague. Not only has she never asked me for permission I last worked with her 11 years ago. It has grown tedious and I admit now that I don't even bother to have a conversation with the prospective employer. I simply say yes I worked with her. Done. So don't put yourself in such a position.