- obtain information about primary mass, e.g. [@abr1; @abr2; @abreu]. A discussion and summary constitutes the last Section 7.

Universality of the angular distributions of electrons
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Universality in earlier papers
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In a pure electromagnetic cascade the shape of the energy spectrum of electrons depends on the cascade age only, being independent of the primary energy; the result obtained analytically. By analogy, Hillas (1982) proposed that the same holds in hadronic extensive air showers, with his new definition of the shower age (Eq. 1). With the help of the shower simulation computer program CORSIKA (Heck et al. 1998) it was possible to show that electron energy spectra were the same in showers with different primary energies once the level considered corresponded to the same shower age (Giller et al. 2004, Nerling et al. 2006). The universal character of the energy spectra has been strenghtened by showing their independence of the primary particle (Giller at al. 2004), and thus, of the high energy interaction model used in the simulations.\
Since the electron angles with respect to the shower axis depend on their energies (the main process responsible being the Coulomb scattering) the following study revealed the universality of the electron 