@article{SF_1980__21_134436,
     author = {P. Olin},
     title = {Varietal free products of bands.},
     journal = {Semigroup forum},
     pages = {83--88},
     publisher = {mathdoc},
     volume = {21},
     year = {1980},
     zbl = {0453.20049},
     url = {http://geodesic.mathdoc.fr/item/SF_1980__21_134436/}
}