This text recommends the use of the hertz (Hz) as the unit of frequency, and the nomenclature to be used for the description of frequency and wavelength bands. It also provides extended information on nomenclature used in some applications.
ITU-R V.431-8-2015 Referenced Document
ITU-R V.430-4 Use of the international system of units (SI)
ITU-R V.431-8 Nomenclature of the frequency and wavelengh bands used in telecommunications