How do you verify that the services on your site are offered by professionals in the field?

Once we receive an application from a Professional, they require to be vetted before we allow them to participate on our site. All must provide 3 references which we check rigorously along with a detailed online search so we can verify that the person is qualified to participate in our field.  Some professionals who are already known and verified by one of our founders may have their references waived as we already know of their reputation and consider them colleagues in this field.