  Let s<t be two fixed positive integers. We study what are the minimum degree
conditions for a bipartite graph G, with both color classes of size n=k(s+t),
which ensure that G has a K_{s,t}-factor. Exact result for large n is given.
Our result extends the work of Zhao, who determined the minimum degree
threshold which guarantees that a bipartite graph has a K_{s,s}-factor.
