M. Jamalizadeh, F. Sharifi, M. H. Moaiyeri, K. Navi, and O. Hashemipour, “Five New MVL Current Mode Differential Absolute Value Circuits Based on Carbon Nano-tube Field Effect Transistors (CNTFETs)”, Nano-Micro Lett, vol. 2, no. 4, pp. 227-234, Nov. 2010.