References
  
  [Bar10]   Barakat,   M.,   The   homalg   package   --   GAP4   (2007-2010),
  ((http://homalg.math.rwth-aachen.de/index.php/core-packages/homalg-package)).
  
  [BLH11]  Barakat,  M.  and  Lange-Hegermann,  M.,  An  axiomatic  setup  for
  algorithmic homological algebra and an alternative approach to localization,
  J. Algebra Appl., 10, 2 (2011), 269--293.
  
  [BR06] Barakat, M. and Robertz, D., mathtthomalg: First steps to an abstract
  package  for  homological  algebra,  in  Proceedings  of  the  X  meeting on
  computational  algebra  and  its  applications  (EACA 2006), Sevilla (Spain)
  (2006),                                                              29--32,
  ((http://homalg.math.rwth-aachen.de/maple/homalg_eaca06.pdf)).
  
  [hpa10]   homalg  project  authors,  T.,  The  homalg  project  (2003-2010),
  ((http://homalg.math.rwth-aachen.de/)).