Columbia subject headings:
Optical instruments--Design and construction--Congresses.
Optical instruments--Testing--Congresses.
Optical materials--Congresses.
Harvard subject headings:
Optical engineering--Congresses.
Optical instruments--Design and construction--Congresses
Optical instruments--Testing--Congresses
Optical materials--Congresses.
Princeton subject headings:
Optical industry--Congresses.
Optical instruments--Design and construction--Congresses.
Optical instruments--Testing--Congresses.