A Comparison of Four Methods for Analog Speech Privacy. - Nuggehally S. Jayant; Barbara J. McDermott; Susan W. Christensen; Ann Marie S. Quinn (IEEE Trans. Commun., 1981)

Analog scramblers for speech based on sequential permutations in time and frequency. - Nikil S. Jayant; Richard V. Cox; Barbara J. McDermott; Ann Marie S. Quinn (Bell Syst. Tech. J., 1983)