@article{ZNSL_1988_174_a6,
     author = {I. N. Ponomarenko},
     title = {Isomorphism problem for classes of graphs closed under contractions},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {147--177},
     publisher = {mathdoc},
     volume = {174},
     year = {1988},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1988_174_a6/}
}