I went one step further.  I asked our main contact from a client company to join me at a speaking event where she described what was happening at their company as a direct result of our services.  It was a win for her because she got the spotlight put on her successful efforts to improve employee experience; it was a win for the organization hosting the event for other leaders in her industry; and it was a win for us because other company leaders got to hear real success stories about the results of our services, from someone other than me.  So try to make the referral process a win for everyone.