@article{ZNSL_1979_88_a13,
     author = {A. V. Proskurin},
     title = {Positive rudimentarity of the graphs of the {Ackermann's} and {Grzegorczyk's} functions},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {186--191},
     publisher = {mathdoc},
     volume = {88},
     year = {1979},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1979_88_a13/}
}