Applicants are also required to submit two required letters of reference which should be submitted to CASPA. References should be as follows: At least one letter/reference must be from a physician assistant (PA). A second letter must be from an additional physician assistant, or physician, dentist, podiatrist, or optometrist, academic advisor, science/mathematics professor, or current/recent employer. If invited to interview, an applicant can only be considered for an alternate and not for full acceptance until letters are received.