@article{CM_1968__20__13_0,
     author = {Curry, Haskell B.},
     title = {The equivalence of two definitions of elementary formal system},
     journal = {Compositio Mathematica},
     pages = {13--20},
     publisher = {Wolters-Noordhoff Publishing},
     volume = {20},
     year = {1968},
     mrnumber = {238671},
     zbl = {0167.01002},
     language = {en},
     url = {http://archive.numdam.org/item/CM_1968__20__13_0/}
}