Given a compact manifold with boundary $(M,\partial M)$. There is a natural pullback map
$$ H^*(M) \to H^*(\partial M) $$
I'm wondering if there is a reference that:
1) constructs this map in Morse cohomology and
2) proves that it agrees with the standard pullback map in cohomology.
I would like to consider Morse functions $f$ such that along a collar neighborhood $\partial M \times [0,1)_r$, $f$ is pulled back from the second factor and $f'(r)< 0$.