Introduction to PSL

The Maple package PSL is an implementation of methods for recognizing groups of L_2-type as epimorphic images of given finitely presented groups.
A finite group H is called to be of L_2-type, if there exist a prime number p and a natural number n, such that H is isomorphic to PSL(2, p^n) or PGL(2, p^n).  
For the succesful performance of PSL the user needs:
- Maple 11 or higher version,
- Maple package Involutive(GINV),
- Maple package PrimDecomp,
- (optional) Magma, Singular or Macaulay2.
For the primary decomposition in positive characteristic we found Magma very reliable.  
The package PSL uses the MAPLE-package Involutive(GINV) and LinearAlgebra[Generic]. Because of the latter one, some procedures of PSL work only in Maple 11 and higher versions.To perform the primary decomposition over integers, which is a crucial part of the algorithm, this package uses the package PrimDecomp by Markus Lange-Hegermann (for computation in characteristic 0) AND one of the four available packages for primary decomposition in positive characteristic: Magma, Singular, Macaulay2 or PrimDecomp.  
Author: Anna Fabiańska, Lehrstuhl B für Mathematik , RWTH Aachen, Germany.
Special thanks to Wilhelm Plesken, Sebastian Jambor, Markus Lange-Hegermann, Daniel Robertz, Mohamed Barakat and Thomas Bächler for contributing with ideas.