@article{SF_1977__15_134236,
     author = {T. Nordahl},
     title = {Free products of normal bands.},
     journal = {Semigroup forum},
     pages = {87--88},
     publisher = {mathdoc},
     volume = {15},
     year = {1977},
     zbl = {0381.20042},
     url = {http://geodesic.mathdoc.fr/item/SF_1977__15_134236/}
}