Sugata Gangopadhyay Deepmala Sharma Sumanta Sarkar Subhamoy Maitra On affine (non)equivalence of Boolean functions. 37-55 2009 85 Computing 1-2 http://dx.doi.org/10.1007/s00607-009-0041-z db/journals/computing/computing85.html#GangopadhyaySSM09