1. Virginia Polytechnic Institute and State University, 200 Patton Hall, Blacksburg, VA 24061, US, e-mail: bernardo@vt.edu.
2. Virginia Polytechnic Institute and State University, 22 Patton Hall, Blacksburg, VA 24061, US, e-mail: tb@vt.edu
3. Tennessee Tech, Box 5015, 1020 Stadium Dr., Cookeville, TN 38505, US, e-mail: dvandenberge@tntech.edu