@article{MAN_1877__12_156787,
     author = {Schr\"oder},
     title = {Note \"uber den {Operationskreis} des {Logikcalculs}},
     journal = {Mathematische Annalen},
     pages = {481--484},
     year = {1877},
     volume = {12},
     url = {http://geodesic.mathdoc.fr/item/MAN_1877__12_156787/}
}