 In other models, e.g. when the electromagnetic field privileges the stationary states of an atom, there is no such comparison with classical equations, and the lack of multi-time distributions becomes a limitation of the model. Such limitations might be overcome by combining models of environmental decoherence with more phenomenological models of ‘continuous measurement’ (as done in a different example by Bhattacharya, Habib and Jacobs 2000). As shown by Brun (2002), the dynamics of stationary states (quantum jumps!) can be obtained from first principles in the decoherent histories formalism. 