References
  
  [BH82]  Brown,  R. and Huebschumann, J. (Brown, R. and Thickstun, T. L.,
  Eds.),   Identities   Among   Relations,  in  Low-Dimensional  Topology,
  Cambridge  University  Press,  London Math. Soc. Lecture Note Series, 46
  (1982), 153-202.
  
  [BS99]  Brown, R. and Razak Salleh, A., On the computation of identities
  among  relations and of free crossed resolutions of groups, London Math.
  Soc. J. Comput. Math., 2 (1999), 28-61.
  
  [Hey99]  Heyworth,  A.,  Applications  of Rewriting Systems and Groebner
  Bases  to  Com  puting  Kan  Extensions  and Identities Among Relations,
  Ph.{D}.~thesis, University of Wales, Bangor (1999).
  
  [HW03]  Heyworth,  A. and Wensley, C. D. (Campbell, C. M., Robertson, E.
  F.  and  Smith,  G.  C.,  Eds.),  Logged  rewriting and identities among
  relators,  in  Groups  St  Andrews  2001 in Oxford, Cambridge University
  Press, London Math. Soc. Lecture Note Series, 304 (2003), 256-276.
  
  
  
  -------------------------------------------------------