L. A. Kochkurov, M. I. Balakin, L. A. Melnikov, V. V. Astakhov, "Numerical modeling of terahertz generation via difference-frequency mixing in two-color laser," Proc. SPIE 8699, Saratov Fall Meeting 2012: Optical Technologies in Biophysics and Medicine XIV; and Laser Physics and Photonics XIV, 869912 (26 February 2013);