@article{MS2_1975__36_166400,
     author = {Clifford J. Earle},
     title = {Some remarks on the {Beltrami} equation.},
     journal = {Mathematica Scandinavica},
     pages = {45--49},
     publisher = {mathdoc},
     volume = {36},
     year = {1975},
     zbl = {0303.30019},
     url = {http://geodesic.mathdoc.fr/item/MS2_1975__36_166400/}
}