  Evolution of a physical quantum state vector is described as governed by two
distinct physical laws: Continuous, unitary time evolution and a
relativistically covariant reduction process. In previous literature, it was
concluded that a relativistically satisfactory version of the collapse
postulate is in contradiction with physical measurements of a non-local state
history. Here it is shown that such measurements are excluded when reduction is
formulated as a physical process and the measurement devices are included as
part of the state vector.
