  Landauer's erasure principle is generalized to nondeterministic processes on
systems having an arbitrary number of non-symmetrical logical states. The
condition that the process is applied in the same way, irrespective of the
initial logical state, imposes some restrictions on the individual heat
exchanges associated with each possible transition. The complete set of such
restrictions are derived by a statistical analysis of the phase-space flow
induced by the process. Landauer's erasure principle can be derived from and is
a special case of these.
