References
  
  [C94]   C.~C.~Sims,   ,  Computation  with  Finitely  Presented  Groups,
  Cambridge University Press (1994)
  
  [EN02]     Eick,     B.     and     Nickel,     W.     ,     Polycyclic,
  http://www.mathematik.tu-darmstadt.de/~nickel/polycyclic/ (2002)
  
  [G59]    G.~Higman,   ,   Some   remarks   on   varieties   of   groups,
  Quart.~J.~Math.~Oxford, 2 (10) (1959), 165--178
  
  [LS90]  Leedham-Green, C. and Soicher, L. , Collection from the left and
  other strategies, J. Symbolic Comput., 9 (5 \& 6) (1990), 665--675
  
  [MW94]  M.~F.~Newman, and Werner~Nickel, , Engel elements in groups, "J.
  Pure Appl. Algebra", 96 (1994), 39--45
  
  [N96]  Nickel,  W. , Computing Nilpotent Quotients of Finitely Presented
  Groups,  in Geometric and Computational Perspectives on Infinite Groups,
  Dimacs  Series in Discrete Mathematics and Theoretical Computer Science,
  25 (1996), 175--191
  
  [V90]  Vaughan-Lee,  M. , Collection from the Left, J. Symbolic Comput.,
  Academic Press, 9 (1990), 725--733
  
  [xxx] GNU MP, http://www.swox.com/gmp/ (2002)
  
  
  
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