NBS Special Publication, Issue 250

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U.S. Government Printing Office, 1965

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Page 11 - Standard Reference Materials issued by the National Bureau of Standards to calibrate a measurement system, or to produce scientific data that can be referred to a common base. A schedule of prices and amounts, as well as directions for ordering, is included.
Page 49 - ... index markers. Since it is necessary to determine the shift of the principal point resulting from prism effect in the lens, the equivalent focal length of the lens as mounted In the camera is incidentally determined...
Page 55 - ... wire loops, spring balances, tension handles, or other attachments liable to be detached or changed in shape. The error in the total length of the tape, when supported horizontally throughout its length at the standard temperature of 68° F. (20° C.) and at standard tension, shall not be more than 0.1 inch per 100 feet (2 mm per 25 m).

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