@article{10_4064_fm_106_1_41_45,
     author = {George Boolos},
     title = {Provability in arithmetic and a schema of {Grzegorczyk}},
     journal = {Fundamenta Mathematicae},
     pages = {41--45},
     publisher = {mathdoc},
     volume = {106},
     number = {1},
     year = {1980},
     doi = {10.4064/fm-106-1-41-45},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/fm-106-1-41-45/}
}