1 J.. Zhou, G.. Taft, C.-P.. Huang, M.. Murnane, H.. Kapteyn, and I.. Christov, Optics Letters 19, (1994).
1 M.T. Asaki, C.-P.. Huang, D.. Garvey, J.. Zhou, H.. Kapteyn, and M.. Murnane, Optics Letters 18, (1993).