  Two quantum systems, each described as a random-matrix ensemble. are coupled
to each other via a number of transition states. Each system is strongly
coupled to a large number of channels. The average transmission probability is
the product of three factors describing, respectively, formation of the first
system from the entrance channel, decay of the second system through the exit
channel, and transport through the transition states. Each of the transition
states contributes a Breit-Wigner resonance. In general, the resonances
overlap.
