In 1971, Professor Chua proposed  that by necessity of symmetry reasons, besides the resistor, the capacitor, and the inductor; a fourth circuit element has to exist. In 2008, members of an HP Lab published  that they successfully realized a nano-scale electronic component. Spice macromodel [3-6] could be a powerful tool for electrical engineers to design and experiment new circuits with memristors.
 L. Chua, “Memristor: The missing circuit element,” IEEE Trans. Circuit Theory, vol. 18, no. 5, pp. 507–519, Sep. 1971.
 D. B. Strukov, G. S. Snider, D. R. Stewart, and S. R. Williams, “The missing memristor found,” Nature, vol. 453, no. 7191, pp. 80–83, May 2008.
 H.H. Li and M. Hu, "Compact Model of Memristors and Its Application in Computing Systems," DATE, 2010.
 Á. Rak and G. Cserey, "Macromodeling of the Memristor in SPICE," IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems, vol. 29, 2010, pp. 632-636.
 D. Batas and H. Fiedler, "A Memristor Spice Implementation and a New Approach for Magnetic Flux Controlled Memristor Modeling," IEEE Transactions on Nanotechnology, 2010, pp. 1-1.
 "Modeling the HP memristor with SPICE," http://www.neurdon.com/2010/07/23/modeling-the-hp-memristor-with-spice/, 2010.