@article{MAN_1989__285_1_164608,
     author = {Pawel Kr\"oger},
     title = {Harmonic spaces associated with parabolic and elliptic differential operators.},
     journal = {Mathematische Annalen},
     pages = {393--404},
     publisher = {mathdoc},
     volume = {285},
     number = {1},
     year = {1989},
     zbl = {0664.31011},
     url = {http://geodesic.mathdoc.fr/item/MAN_1989__285_1_164608/}
}