  
  [1X1 [33X[0;0YIntroduction[133X[101X
  
  [33X[0;0YThe  purpose  of  this  package  is  to provide functionalities to work with
  torsion  units  in  (integral)  group rings. It implements a method that was
  developed  by  I.S. Luthar and I.B.S. Passi in [LP89] and which was extended
  by  M.  Hertweck  in  [Her07].  These  names also constitute the name of the
  method,  suggested by O. Konovalov: [13XHe[113Xrtweck-[13XL[113Xuthar-[13XP[113Xassi. The theory behind
  the  method is briefly described in Chapter [14X5[114X and also in the survey article
  [BM18].[133X
  
  [33X[0;0YThe package uses the software 4ti2 [tea] and/or normaliz [BIR+] and hence is
  only  properly  working  on  systems  which  have  at  least  one of the two
  installed.  Some  functions  though work without any of the two and they are
  available  even  if  none of the packages 4ti2Interface or NormalizInterface
  can  be  loaded.  normaliz  is  usually  automatically  installed  with  the
  GAP-package  NormalizInterface,  see  the  documentation of that package for
  details.  For  more  information  on  4ti2  and to download it, please visit
  4ti2.github.io  ([7Xhttps://4ti2.github.io[107X).  To  interact  with these external
  software  the package makes use of the 4ti2-Interface and normaliz-Interface
  written by S. Gutsche, C. Söger and M. Horn. The 4ti2-Interface in turn uses
  the  package  IO, that needs a C-part to be compiled; see the readme-file or
  the  documentation  of the IO-package for details. The package also provides
  the  possibility  to  use  redund  from the lrslib software [Avi], to remove
  redundant  inequalities  before solving the system, which might speed up the
  computations  significantly  when  4ti2  is  used.  However,  it  is  not  a
  requirement  to  have lrslib installed. If the above mentioned preconditions
  are   fulfilled,   one  just  has  to  copy  the  HeLP-package  in  the  GAP
  pkg-directory.  Now the package can be loaded by typing [9XLoadPackage("HeLP");[109X
  during  a  GAP-session.  If  the  HeLP-package doesn't work properly on your
  computer, you might want to check Section [14X6.1[114X for some trouble shooting.[133X
  
