You must be a member of the APS to be a member of the Topical Group. The additional cost to join the Topical Group is $6.00. Joining is most conveniently done when you renew your APS membership. If you are not yet a member of the APS, look here for information on how to join. If you have already renewed your APS membership and don't want to wait until the next renewal to join the Topical Group, look here.