@incollection{AST_1980__75-76__167_0,
     author = {Kupka, Ivan},
     title = {Some problems in accessibility theory},
     booktitle = {Analyse des syst\`emes},
     series = {Ast\'erisque},
     pages = {167--176},
     publisher = {Soci\'et\'e math\'ematique de France},
     number = {75-76},
     year = {1980},
     mrnumber = {581713},
     zbl = {0458.93004},
     language = {en},
     url = {http://www.numdam.org/item/AST_1980__75-76__167_0/}
}