an Entity references as follows:
Scattering of radiation is its deflection from its incident path without loss of energy. Backwards scattering refers to the sum of scattering into all backward angles i.e. scattering_angle exceeding pi/2 radians. A scattering_angle should not be specified with this quantity. "Backscattering ratio" is the ratio of the quantity with standard name volume_attenuated_backwards_scattering_function_in_air to the quantity with standard name volume_attenuated_backwards_scattering_function_in_air_assuming_no_aerosol_or_cloud. "histogram_of_X[_over_Z]" means histogram (i.e. number of counts for each range of X) of variations (over Z) of X. The data variable should have an axis for X.