DIN 51423-2
DIN 51423-2 Testing of mineral oils - Part 2: Measurement of the relative refractive index with the Abbe-refractometer
standard by Deutsches Institut Fur Normung E.V. (German National Standard), 02/01/2010
standard by Deutsches Institut Fur Normung E.V. (German National Standard), 02/01/2010