These models can be used only for a extragalactic source,
whose redshift is known.
The amplitude A of these models is normalized to a luminosity
(unit 
keV/s) in a given energy interval
, defined in the observer frame.
This does not prove right for models whose integral is finite.
In this case the integration boundaries 
and 
are fixed to plus and minus infinity.
The luminosity distance 
is calculated according
to the Friedmann-Lemaitre cosmological model.
Default values of the parameters are 
= 50km/s/Mpc
and 
= 0.5
