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Let M,N and B⊂ N be compact smooth manifolds of dimensions
n+k,n and l, respectively. Given a map f:M →
N, we give homological conditions under which g-1(B) has
nontrivial cohomology (with local coefficients) for any map g
homotopic to f. We also show that a certain cohomology class in
Hj(N,N-B) is Poincaré dual (with local coefficients) under
f* to the image of a corresponding class in Hn+k-j(f-1(B))
when f is transverse to B. This generalizes a similar formula of
D Gottlieb in the case of simple coefficients.
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