@article{10_4007_annals_2005_162_943,
     author = {Joseph J. Kohn and Makhlouf Derridj and David S. Tartakoff},
     title = {Hypoellipticity and loss of derivatives (with an {Appendix} by {Makhlouf} {Derridj} and {David} {S.} {Tartakoff)}},
     journal = {Annals of mathematics},
     pages = {943--986},
     publisher = {mathdoc},
     volume = {162},
     number = {2},
     year = {2005},
     doi = {10.4007/annals.2005.162.943},
     mrnumber = {2183286},
     zbl = {1107.35044},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4007/annals.2005.162.943/}
}