1. Allen (R. G. D.) (1955): “The Engineer’s Approach to Economic Models”, Economica, 22, 158–68.
2. Bothwell (F. E.) (1952): “The Method of Equivalent Linearization”, Econometrica, 20, 269–83.
3. Brown (G. S.) and Campbell (D. P.) (1948): Principles of Servomechanisms (Wiley, 1948).
4. Carslaw (H. S.) and Jaeger (J. C.) (1941, 1948): Operational Methods in Applied Mathematics (Oxford, First Ed. 1941, Second Ed. 1948).
5. Frisch (R.) (1933): “Propagation Problems and Impulse Problems in Dynamic Economics”, in Economic Essays in Honour of Gustav Cassel (Allen and Unwin, 1933).