1 A.S. Sandhu, E.. Gagnon, R.. Santra, V.. Sharma, W.. Li, P.. Ho, P.. Ranitovic, C.L. Cocke, M.. Murnane, and H.. Kapteyn, Science 322, (2008).
1 A.. Larson, S.. Tonzani, R.. Santra, and C.H. Greene, Journal of Physics: Conference Series 4, (2005).