Sotner, Roman, Jan Jerabek, Tomas Dostal, and Kamil Vrba. “Z-Copy Voltage Controlled Current Follower Differential Input Transconductance Amplifier in Controllable Biquadratic Band-Pass Filter”. Elektronika ir Elektrotechnika 22, no. 4 (August 9, 2016): 32 - 36. Accessed February 25, 2021. https://eejournal.ktu.lt/index.php/elt/article/view/15911.