@article{10_4064_cm_41_1_117_121,
     author = {L. R. Hunt and J. J. Murray and M. J. Strauss},
     title = {Liouville's theorem for first-order partial differential operators},
     journal = {Colloquium Mathematicum},
     pages = {117--121},
     publisher = {mathdoc},
     volume = {41},
     number = {1},
     year = {1979},
     doi = {10.4064/cm-41-1-117-121},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/cm-41-1-117-121/}
}