Veklenko, B. A., Y. I. Malachov, C. S. Nguyen, and C. S. Nguyen. “Superluminal Signals in Quantum Optics”. Theory and Applications of Physical Science Vol. 1, Nov. 2019, pp. 45-65, https://stm1.bookpi.org/index.php/taps-v1/article/view/651.