S. Albeverio et A. Daletskii, ALGEBRAS OF PSEUDODIFFERENTIAL-OPERATORS IN L-2 GIVEN BY SMOOTH MEASURES ON HILBERT-SPACES, Mathematische Nachrichten, 192, 1998, pp. 5-22
Pseudodifferential operators with symbols on a Hilbert phase space are
defined as symmetric operators in L-2 given by a smooth measure. The
main formulae of symbolic calculus are proved in this context.