@article{CM_1969__21_3_292_0,
     author = {Homagk, Fritz},
     title = {Ein intuitionistischer Beweis f\"ur den Graphensatz von D. Koenig},
     journal = {Compositio Mathematica},
     publisher = {Wolters-Noordhoff Publishing},
     volume = {21},
     number = {3},
     year = {1969},
     pages = {292-294},
     zbl = {0205.00501},
     mrnumber = {266793},
     language = {de},
     url = {http://www.numdam.org/item/CM_1969__21_3_292_0}
}

Homagk, Fritz. Ein intuitionistischer Beweis für den Graphensatz von D. Koenig. Compositio Mathematica, Volume 21 (1969) no. 3, pp. 292-294. http://www.numdam.org/item/CM_1969__21_3_292_0/