Shewell, John Robert (1959). "On the Formation of Quantum-Mechanical Operators". American Journal of Physics. 27 (1). American Association of Physics Teachers (AAPT): 16–21. Bibcode:1959AmJPh..27...16S. doi:10.1119/1.1934740. ISSN0002-9505.
Shewell, John Robert (1959). "On the Formation of Quantum-Mechanical Operators". American Journal of Physics. 27 (1). American Association of Physics Teachers (AAPT): 16–21. Bibcode:1959AmJPh..27...16S. doi:10.1119/1.1934740. ISSN0002-9505.
Shewell, John Robert (1959). "On the Formation of Quantum-Mechanical Operators". American Journal of Physics. 27 (1). American Association of Physics Teachers (AAPT): 16–21. Bibcode:1959AmJPh..27...16S. doi:10.1119/1.1934740. ISSN0002-9505.