DIN 5493-2
DIN 5493-2 Logarithmic quantities and units - Part 2: Logarithmic ratios, levels in nepers and decibels
standard by Deutsches Institut Fur Normung E.V. (German National Standard), 09/01/1994
standard by Deutsches Institut Fur Normung E.V. (German National Standard), 09/01/1994