@article{AIF_1992__42_4_805_0, author = {Artino, R. A. and Barros-Neto, J.}, title = {Matrix triangulation of hypoelliptic boundary value problems}, journal = {Annales de l'Institut Fourier}, pages = {805--824}, publisher = {Institut Fourier}, address = {Grenoble}, volume = {42}, number = {4}, year = {1992}, doi = {10.5802/aif.1310}, zbl = {0758.35098}, mrnumber = {93k:35287}, language = {en}, url = {https://aif.centre-mersenne.org/articles/10.5802/aif.1310/} }