1. Horowitz, P., and Hill, W.: ‘The art of electronics’, (Cambridge University Press, Cambridge, UK 1991)
2. Tietze, U., and Schnek, C.K.: ‘Electronics circuits: design and applications’, (Springer, Berlin, Germany 1991), p. 795–796
3. A simple wide-band sine wave quadrature oscillator
4. An integrable gm-C quadrature oscillator
5. The Utility of the All-Pass Filter