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@incollection{JEDP_1982____A15_0, author = {Stein, Elias M.}, title = {An example of the {Heisenberg} group}, booktitle = {}, series = {Journ\'ees \'equations aux d\'eriv\'ees partielles}, eid = {15}, pages = {1--3}, publisher = {\'Ecole polytechnique}, year = {1982}, zbl = {0497.35069}, language = {en}, url = {http://geodesic.mathdoc.fr/item/JEDP_1982____A15_0/} }
Stein, Elias M. An example of the Heisenberg group. Journées équations aux dérivées partielles (1982), article no. 15, 3 p. http://geodesic.mathdoc.fr/item/JEDP_1982____A15_0/