@article{ITA_2005__39_1_239_0,
     author = {Pin, Jean-\'Eric and Straubing, Howard},
     title = {Some results on $\mathcal {C}$-varieties},
     journal = {RAIRO - Theoretical Informatics and Applications - Informatique Th\'eorique et Applications},
     pages = {239--262},
     publisher = {EDP-Sciences},
     volume = {39},
     number = {1},
     year = {2005},
     doi = {10.1051/ita:2005014},
     mrnumber = {2132590},
     zbl = {1083.20059},
     language = {en},
     url = {http://www.numdam.org/articles/10.1051/ita:2005014/}
}