Fedii V S

Publications in Math-Net.Ru

1. An example of a second-order nonhypoelliptic operator with the property of global hypoellipticity
   
   Mat. Zametki, 12:3 (1972),  269–274
2. On a criterion for hypoellipticity
   
   Mat. Sb. (N.S.), 85(127):1(5) (1971),  18–48
3. Estimates in the $H_{(s)}$ norms, and hypoellipticity
   
   Dokl. Akad. Nauk SSSR, 193:2 (1970),  301–303