Journal of Automata, Languages and Combinatorics

@article{jalc160105,
  author  = {Sherzod~Turaev and Mohd Hasan~Selamat and Mohamed~Othman},
  title   = {Nonterminal Complexity of Tree Controlled Grammars Generating Context-Free Languages},
  journal = jalc,
  year    = 2011,
  volume  = 16,
  number  = {1},
  pages   = {55--63}
}