Michaël Quisquater Bart Preneel Joos Vandewalle Spectral characterization of cryptographic Boolean functions satisfying the (extended) propagation criterion of degree <i>l</i> and order <i>k</i>. 25-28 2005 93 Inf. Process. Lett. 1 http://dx.doi.org/10.1016/j.ipl.2004.08.011 db/journals/ipl/ipl93.html#QuisquaterPV05