@article{GDZPPN002429608,
title = {Compatibility Operators for Degenerate Elliptic Equations on the Ball and Heisenberg Groups.},
journal = {Mathematische Zeitschrift},
volume = {185},
year = {1984},
pages = {289-304},
zbl = {0538.47031},
url = {http://dml.mathdoc.fr/item/GDZPPN002429608}
}
Graham, C. Robin. Compatibility Operators for Degenerate Elliptic Equations on the Ball and Heisenberg Groups.. Mathematische Zeitschrift, Tome 185 (1984) pp. 289-304. http://gdmltest.u-ga.fr/item/GDZPPN002429608/