@article{SF_1972__4_133891,
     author = {T. Evans},
     title = {When is a functionally free algebra free?},
     journal = {Semigroup forum},
     pages = {177--184},
     publisher = {mathdoc},
     volume = {4},
     year = {1972},
     zbl = {0255.08004},
     url = {http://geodesic.mathdoc.fr/item/SF_1972__4_133891/}
}