1. P. Albano, A. Bove, The presence of symplectic strata improves the Gevrey regularity for sums of squares, preprint, 2013.
2. Pseudo-differential operators and Gevrey classes;Boutet de Monvel;Ann. Inst. Fourier (Grenoble),1967
3. Opérateurs pseudo-différentiels analytiques et opérateurs dʼordre infini;Boutet de Monvel;Ann. Inst. Fourier (Grenoble),1972
4. Hypoellipticity and non hypoellipticity for sums of squares of complex vector fields;Bove;Anal. PDE,2013
5. Gevrey hypoellipticity for an interesting variant of Kohnʼs operator;Bove,2010