@article{MZ_1969__111_171200,
     author = {Reuben Sandler},
     title = {On {Free} {Extensions} of {Rank} 1.},
     journal = {Mathematische Zeitschrift},
     pages = {233--248},
     publisher = {mathdoc},
     volume = {111},
     year = {1969},
     zbl = {0176.17704},
     url = {http://geodesic.mathdoc.fr/item/MZ_1969__111_171200/}
}