1. Fifer, S.: Analogue Computation, (McGraw-Hill, New york 1961)
2. Fifer, S.: Analogue Computation, (McGraw-Hill, New york 1961),2, p. 583
3. Fifer, S.: Analogue Computation, (McGraw-Hill, New york 1961),3, p. 835
4. Fifer, S.: Analogue Computation, (McGraw-Hill, New york 1961),3, p. 851