@article{SF_1970__1_133779,
     author = {T. Tamura},
     title = {Finite union of commutative power joined semigroups.},
     journal = {Semigroup forum},
     pages = {75--84},
     publisher = {mathdoc},
     volume = {1},
     year = {1970},
     zbl = {0195.03501},
     url = {http://geodesic.mathdoc.fr/item/SF_1970__1_133779/}
}