@incollection{AST_1980__75-76__87_0,
     author = {Ferfera, Abdelhak},
     title = {Combinatoire du mono{\"\i}de libre et composition de certains syst\`emes non lin\'eaires},
     booktitle = {Analyse des syst\`emes},
     series = {Ast\'erisque},
     pages = {87--93},
     publisher = {Soci\'et\'e math\'ematique de France},
     number = {75-76},
     year = {1980},
     mrnumber = {581705},
     zbl = {0458.93028},
     language = {fr},
     url = {http://archive.numdam.org/item/AST_1980__75-76__87_0/}
}