Department of Applied Mathematics, Zhejiang A&F University, Hangzhou 311300, China
Copyright © 2010 Guang-Hui Xu. This is an open access article distributed under the
Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Let be a simple graph with vertices, and let be the least eigenvalue of . The connected graphs in which the number of edges equals the number of vertices are called unicyclic graphs. In this paper, the first five unicyclic graphs on order in terms of their smaller least eigenvalues are determined.