  A general formulation of zero curvature connections in a principle bundle is
presented and some applications are discussed. It is proved that a related
connection based on a prolongation in an associated bundle remains zero
curvature as well. It is also shown that the connection coefficients can be
defined so that the partial differential equation to be studied appears as the
curvature term in the structure equations. It is discussed how Lax pairs and
Backlund transformations can be formulated for such equations. It is discussed
how Lax pairs and Backlund transformations can be formulated for such equations
that occur as zero curvature terms.
