Columbia subject headings:
Gauge invariance--Congresses.
Quantum electrodynamics--Congresses.
Quantum optics--Congresses.
Harvard subject headings:
Gauge invariance--Congresses.
Quantum electrodynamics--Congresses.
Quantum optics--Congresses.
Princeton subject headings:
Gauge invariance--Congresses.
Quantum electrodynamics--Congresses.
Quantum optics--Congresses.