Parmeggiani, A. Spectral theory of non-commutative harmonic oscillators: an introduction [Electronic resource] / A. Parmeggiani. - Electronic text data. - Berlin ; Heidelberg : Springer, 2010. - (Lecture notes in mathematics, ISSN 0075-8434 ; 1992). - ISBN 978-3-642-11922-4 : Б. ц.