Direct observation of betatron oscillations in a laser-plasma electron acceleratorY. Glinec, J. Faure, A. Lifschitz, J. M. Vieira, R A. Fonseca, L. O. Silva and V. MalkaEPL, 81 6 (2008) 64001DOI: https://doi.org/10.1209/0295-5075/81/64001