@article{IM_1973__21_142225,
     author = {Lars H\"ormander},
     title = {On the {Existence} of {Real} {Analytic} {Solutions} of {Partial} {Differential} {Equations} with {Constant} {Coefficients.}},
     journal = {Inventiones mathematicae},
     pages = {151--182},
     publisher = {mathdoc},
     volume = {21},
     year = {1973},
     zbl = {0282.35015},
     url = {http://geodesic.mathdoc.fr/item/IM_1973__21_142225/}
}