Khabibullin, R.A., N.V. Shchavruk, D.S. Ponomarev, D.V. Ushakov, A.A. Afonenko, K.V. Maremyanin, O.Yu. Volkov, V.V. Pavlovskiy, and A.A. Dubinov. 2019. “The Operation of THz Quantum Cascade Laser in the Region of Negative Differential Resistance”. Opto-Electronics Review 27 (4):329-33. https://doi.org/10.1016/j.opelre.2019.11.002.