 Let us close this section with two additional remarks about weak measurements, including the hybrid case. First, there is an abundant literature in which weak measurements are discussed in terms of so-called weak values of certain quantum observables. The physical significance (if any) of weak values has been the subject of an ongoing controversy. Without entering that discussion it is worth pointing out that apart from exceptional cases a weak value has nothing to do with a quantum property in the sense used in the histories interpretation, related to some subspace of the quantum Hilbert space; e.g., one of the \(\xi^{jk}\) in .