@article{ZNSL_1969_16_a18,
     author = {N. V. Petri},
     title = {Two theorems on the complexity of algorithms and computations},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {165--174},
     publisher = {mathdoc},
     volume = {16},
     year = {1969},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1969_16_a18/}
}