@article{ZNSL_1971_20_a22,
     author = {G. S. Tseitin},
     title = {The lower estimate of number of steps for reversing normal algorithms and other similar algorithms},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {243--262},
     publisher = {mathdoc},
     volume = {20},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1971_20_a22/}
}