1. The product formula for semigroups defined by Friedrichs extensions;Faris;Pacific J. Math.,1967
2. Functional Analysis and Semigroups;Hille,1957
3. General Topology;Kelley,1955
4. Feynman integrals and the Schrödinger equation;Nelson;J. Math. Phys.,1964
5. Notes toward the construction of nonlinear relativistic quantum fields, I;Segal,1967