  Destructive quantum interference (DQI) and its effects on electron transport
is studied in chemical molecules and finite physical lattices that can be
described by a discrete Hamiltonian. Starting from a bipartite system whose
conductance zeros are known to exist between any two points of a specially
designated set, the interference set, we use the Dyson equation to develop a
general algorithm of determining the zero conductance points in complex
systems, which are not necessarily bipartite. We illustrate this procedure as
it applies to the fulvene molecule. The stability of the conductance zeros is
analyzed in respect with external perturbations.
