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

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