@article{10_21136_CMJ_1988_102241,
     author = {Cherubini, Alessandra and Varisco, Ada},
     title = {On $E_k$-rings},
     journal = {Czechoslovak Mathematical Journal},
     pages = {456--463},
     publisher = {mathdoc},
     volume = {38},
     number = {3},
     year = {1988},
     doi = {10.21136/CMJ.1988.102241},
     mrnumber = {950299},
     zbl = {0673.16009},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/CMJ.1988.102241/}
}