Uiberacker, M., Uphues, Th., Schultze, M., Verhoef, A., Yakovlev, V., Kling, M. F., Rauschenberger, J., Kabachnik, N. M., Schröder, H., Lezius, M., Kompa, K. L., Müller, H.-G., Vrakking, M. J. J., Hendel, S., Kleineberg, U., Heinzmann, U., Drescher, M., & Krausz, F. (2007). Attosecond real-time observation of electron tunnelling in atoms. Nature, 446(7136), 627–632. https://doi.org/10.1038/nature05648