The paper Optical Third-Harmonic Generation in Hexagonal Boron Nitride Thin Films written by Anna A. Popkova, Ilya M. Antropov, Johannes E. Fröch, Sejeong Kim, Igor Aharonovich, Vladimir O. Bessonov, Alexander S. Solntsev, and Andrey A. Fedyanin has been published in ACS Photonics.