Incompressible surfaces in handlebodies

Let F 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 F×I. It also supplies a simple sufficient condition for when 2-sided surfaces in this form are incompressible. Since F×I is a handlebody when F has boundary, the paper applies to incompressible surfaces in handlebodies.