1. DEPARTMENT OF MATHEMATICS AND STATISTICS UNIVERSITY OF NEBRASKA KEARNEY NEBRASKA
2. DEPARTMENT OF MATHEMATICS UNIVERSITY OF RHODE ISLAND KINGSTON RHODE ISLAND
3. MATHEMATICS DEPARTMENT RYERSON UNIVERSITY TORONTO ONTARIO CANADA
4. MATHEMATICS DEPARTMENT, ZHEJIANG NORMAL UNIVERSITY, JINHUA, ZHEJIANG, CHINA AND, MATHEMATICS DEPARTMENT UNIVERSITY OF ILLINOIS URBANA ILLINOIS