Copyright © 2010 Fengqin Zhang and Jurang Yan. 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.
Resonance and nonresonance periodic value problems of first-order
differential systems are studied. Several new existence and uniqueness of solutions
for the above problems are obtained. To establish such results sufficient
conditions of limit forms are given. A necessary and sufficient condition for
existence of nontrivial solution is also proved.