[EGN] Eick, B., G\"ahler, F. and Nickel, W. cryst, \URL{http://www.gap-system.org/Packages/cryst.html}
[Ell] Ellis, G. HAP, \URL{http://hamilton.nuigalway.ie/Hap/www/}
[GJ] Gawrilow, E. and Joswig, M. polymake, \URL{http://www.math.tu-berlin.de/polymake/}
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