@article{05198134, title = {Positivity in twisted convolution algebra and Fourier modulation spaces.}, journal = {Bulletin. Classe des Sciences Math\'ematiques et Naturelles. Sciences Math\'ematiques}, volume = {133}, year = {2006}, pages = {75-86}, doi = {10.2298/BMAT0631010T}, zbl = {1119.47040}, language = {en}, url = {http://dml.mathdoc.fr/item/05198134} }
Toft, J. Positivity in twisted convolution algebra and Fourier modulation spaces.. Bulletin. Classe des Sciences Mathématiques et Naturelles. Sciences Mathématiques, Tome 133 (2006) pp. 75-86. doi : 10.2298/BMAT0631010T. http://gdmltest.u-ga.fr/item/05198134/