  In this paper we discuss topological BF theories in 3 and 4 dimensions.
Observables are associated to ordinary knots and links (in 3 dimensions) and to
2-knots (in 4 dimensions). The vacuum expectation values of such observables
give a wide range of invariants. Here we consider mainly the 3-dimensional
case, where these invariants include Alexander polynomials, HOMFLY polynomials
and Kontsevich integrals.
