Kk. Wan et al., OBSERVABLES, MAXIMAL SYMMETRICAL OPERATORS AND POV MEASURES IN QUANTUM-MECHANICS, Journal of physics. A, mathematical and general, 28(8), 1995, pp. 2379-2393
There has been a lot of interest in generalizing orthodox quantum mech
anics to include pov measures as observables, namely as unsharp observ
ables. Such pov measures are related to symmetric operators. The prese
nt paper examines how symmetric operators arise and how they can repre
sent observables.