@article{ZNSL_1969_16_a16,
     author = {V. P. Orevkov},
     title = {On non-lengthening applications of equality rules},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {152--156},
     publisher = {mathdoc},
     volume = {16},
     year = {1969},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1969_16_a16/}
}