@article{ITA_1983__17_4_331_0,
     author = {Knast, Robert},
     title = {Some theorems on graph congruences},
     journal = {RAIRO. Informatique th\'eorique},
     pages = {331--342},
     publisher = {EDP-Sciences},
     volume = {17},
     number = {4},
     year = {1983},
     mrnumber = {743893},
     language = {en},
     url = {http://www.numdam.org/item/ITA_1983__17_4_331_0/}
}