Combining the symbol values from the [SenML Units] "SenML Units"
      registry and the [Secondary Units] "Secondary Units" registry in [IANA the "Sensor
      Measurement Lists (SenML)" registry senml] group [IANA.senml] as
      specified by Sections 4.5.2 and 12.1 of [RFC8428] and Section 3 of
      [RFC8798], respectively (which (which, by the registration policy policy, are
      guaranteed to be non-overlapping).