@article{MSH_1969__26__5_0,
     author = {Kreweras, G.},
     title = {D\'enombrements syst\'ematiques de relations binaires externes},
     journal = {Math\'ematiques et sciences humaines},
     pages = {5--15},
     publisher = {Ecole Pratique des hautes \'etudes, Centre de math\'ematique sociale et de statistique},
     volume = {26},
     year = {1969},
     mrnumber = {265183},
     zbl = {0206.02301},
     language = {fr},
     url = {http://archive.numdam.org/item/MSH_1969__26__5_0/}
}