Documentation:
ELMAG is a Monte Carlo program for the simulation of electromagnetic cascades
initiated by high-energy photons and electrons interacting with the
extragalactic background light. Its original version was written by
M. Kachelrieß, S. Ostapchenko and R. Tomàs. This version is
decribed in M. Kachelrieß, S. Ostapchenko and R. Tomàs,
Comput.Phys.Commun. 183 (2012) 1036-1043
available on the arxiv or here as a
pdf file.
The version 3.01 is decribed in M. Blytt, M. Kachelrieß and S. Ostapchenko, Comput.Phys.Commun. 252 (2020) 107163, preprint arXiv:1909:09210, available on the arxiv.
For an updated manual for the current version 3.03 see here.