@inbook{inbook2cbe02d0,
title   = {Symplectic strata and analytic hypoellipticity},
author = {Cordaro, Paulo Domingos and Hanges, Nicholas},
year = {2006},
doi = {10.1007/978-0-8176-4521-2_7},
publisher = {Birkhäuser},
journal   = {Phase space analysis of partial differential equations}
}