@article{SEMR_2006_3_a15,
     author = {D. V. Solomatin},
     title = {Direct products of cyclic semigroups admitting a~planar {Caley} graph},
     journal = {Sibirskie \`elektronnye matemati\v{c}eskie izvesti\^a},
     pages = {238--252},
     publisher = {mathdoc},
     volume = {3},
     year = {2006},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/SEMR_2006_3_a15/}
}