@article{10_14712_1213_7243_2015_122,
     author = {Rojas-Hern\'andez, Reynaldo},
     title = {$\Sigma_s$-products revisited},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {243--255},
     publisher = {mathdoc},
     volume = {56},
     number = {2},
     year = {2015},
     doi = {10.14712/1213-7243.2015.122},
     mrnumber = {3338737},
     zbl = {06433822},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.14712/1213-7243.2015.122/}
}