“Laser-induced molybdenum oxide formation by low energy (nJ)-high repetition rate (MHz) femtosecond pulses” M. Cano-Lara, S. Camacho-Lopez, A. Esparza-Garcia. M. A. Camacho-Lopez. Opt. Mat. 33, 1648-1653 (2011). http://dx.doi.org/10.1016/j.optmat.2011.04.029