A Standard Form for Incompressible Surfaces in a Handlebody
Linda E. Green
Let $\Sigma$ be a compact surface and let $I$ be the unit interval. This paper gives a standard form for all 2-sided incompressible surfaces in the 3-manifold $\Sigma \times I$. Since $\Sigma \times I$ is a handlebody when $\Sigma$ has boundary, this standard form applies to incompressible surfaces in a handlebody.