1. et al. ‘Describing function inversion: theory and computational techniques’, Purdue University, Control & Information, Systems Laboratory, December, 1962
2. Gibson, J.E.: Nonlinear automatic control, (McGraw-Hill, Kogakusha, Tokyo 1963), p. 565–571
3. Lamba, S.S.: ‘Synthesis and applications of nonlinear multimodal system’, 1968, Ph.D. thesis, University of New Brunswick, Department of Electrical Engineering, Canada