@Article{	  DiekertW13,
  title		= "{C}ontext-{F}ree {G}roups and {T}heir {S}tructure {T}rees",
  journal	= "International Journal of Algebra and Computation",
  volume	= "23",
  pages		= "611--642",
  year		= "2013",
  author	= "Diekert, Volker and Wei{\ss}, Armin",
  url		= "http://dx.doi.org/10.1142/S0218196713500124",
  doi		= "10.1142/S0218196713500124"
}