1. A. A. Voronov, Elements of the Theory of Automatic Control [in Russian], Voenizdat, Moscow (1954).
2. P. M. Morse and H. Feshbach, Methods of Theoretical Physics, Vols. 1 and 2, McGraw-Hill, New York (1953).
3. I. M. Nunzioto, ?On heat conduction in materials with memory,? Quart. Appl. Math., 187 (July, 1971).
4. A. V. Lykov, Inzh.-Fiz. Zh.,26, No. 5 (1974).
5. G. Doetsch, Guide to the Application of Laplace and Z Forms, Van Nostrand Reinhold.