@article{MS2_1961__9_165767,
     author = {Bjarni Jonsson and Alfred Tarski},
     title = {On {Two} {Properties} of {Free} {Algebras.}},
     journal = {Mathematica Scandinavica},
     pages = {95--101},
     publisher = {mathdoc},
     volume = {9},
     year = {1961},
     zbl = {0111.02002},
     url = {http://geodesic.mathdoc.fr/item/MS2_1961__9_165767/}
}