MaurerSW82'

@article{DBLP:journals/jacm/MaurerSW82,
  author    = {Hermann A. Maurer and
               Arto Salomaa and
               Derick Wood},
  title     = {Dense Hierarchies of Grammatical Families},
  journal   = {J. ACM},
  volume    = {29},
  number    = {1},
  year      = {1982},
  pages     = {118-126},
  ee        = {http://doi.acm.org/10.1145/322290.322298},
  bibsource = {DBLP, http://dblp.uni-trier.de}
}