@article{10_4064_aa149_4_5,
     author = {Christopher Frei},
     title = {Sums of units in function fields {II:
} {The} extension problem},
     journal = {Acta Arithmetica},
     pages = {361--369},
     publisher = {mathdoc},
     volume = {149},
     number = {4},
     year = {2011},
     doi = {10.4064/aa149-4-5},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/aa149-4-5/}
}