@article{CMUC_1987__28_3_a18,
     author = {P\"oschel, Reinhard and Wessel, Walter},
     title = {Classes of graphs definable by graph algebra identities or quasi-identities},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {581--592},
     publisher = {mathdoc},
     volume = {28},
     number = {3},
     year = {1987},
     mrnumber = {912586},
     zbl = {0621.05030},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1987__28_3_a18/}
}