References
  
  [BR08] Barakat, M. and Robertz, D., homalg -- A Meta-Package for Homological
  Algebra, J. Algebra Appl., 7, 3 (2008), 299--317, ((arXiv:math.AC/0701146)).
  
  [MR01]  McConnell, J. C. and Robson, J. C., Noncommutative Noetherian rings,
  American   Mathematical   Society,  Revised  edition,  Graduate  Studies  in
  Mathematics, 30, Providence, RI (2001), xx+636 pages, ((With the cooperation
  of L. W. Small)).