@techreport{TUW-103153, author = {Hlawatsch, Franz and Papandreou-Suppappola, A. and Boudreaux-Bartels, G.F.}, title = {The power classes: Quadratic time-frequency representations with scale covariance and dispersive time-shift covariance}, institution = {E389 - Institute of Telecommunications; Vienna University of Technology}, year = {1997} }