Ultrafast low-energy dynamics of graphite studied by nonlinear multi-THz spectroscopy C. Schmidt, B. Mayer, F. Junginger, M. Rebholz, A. Grupp, D. Brida, R. Huber, A. Leitenstorfer and A. Pashkin EPJ Web of Conferences, 41 (2013) 04023 Published online: 13 March 2013 DOI: 10.1051/epjconf/20134104023