Nomura, Yutaka Laboratory for Attosecond Physics, Max Planck Institute of Quantum Optics, Max Planck Society;
Nomura, Y., Kanai, T., Minemoto, S., & Sakai, H. (2007). Efficient generation of high-order sum and difference frequencies in the xuv region by combining a weak longer-wavelength field. Physical Review A, 75: 041801. doi:10.1103/PhysRevA.75.041801.