1. Department of Mathematics; Idaho State University; 921 S. 8th Avenue, Stop 8085, Pocatello ID 83209-8085 U.S.A.
2. Center for Bioinformatics and Computational Genomics; Georgia Institute of Technology; 313 Ferst Drive, Suite 2127 Atlanta GA 30332 U.S.A.
3. Department of Applied Mathematics; St. Petersburg State Polytechnical University; Polytechnicheskaya ul. 29 195251 St. Petersburg Russia