The paper deals with the
question about the existence or non-existence of a degree-one map of a closed
orientable 3-manifold M to some lens space. The answer to this question is
determined by the cyclic decomposition of H1(M), except when H1(M) contains an
even number of direct factors isomorphic to Z2k. In this case one has to calculate the
linking matrix of M to get the answer. For every n even, we give a Seifert manifold
Mn with H1(Mn)≅Zn⊕Zn that does not admit a degree-one map to L(n,m) for any
m.