 With regard to the former case, environmental decoherence can be easily described also in terms of decoherent histories. One needs to take times that are separated by intervals larger than the decoherence time scale, and projections onto the preferred states. Then the environmental monitoring ensures that the resulting histories decohere. (In case of a continuous set of preferred states, one might need to generalise the histories formalism slightly, using ‘effects’ rather than projections; see e.g. Kent 1998.) In this sense, environmental decoherence can be seen as a special case of decoherent histories, but the descriptions given by the two formalisms are somewhat different. While decoherent histories define multi-time distributions over the preferred states (at discrete times), models of environmental decoherence essentially describe single-time distributions over the preferred states. While they have the advantage of being well-defined at all times, these single-time distributions do not explicitly describe any temporal evolution at the level of the individual components. 