Qiao, B., Zepf, M., Gibbon, P., Borghesi, M., Dromey, B., Kar, S., Schreiber, J., & Geissler, M. (2011). Conditions for efficient and stable ion acceleration by moderate circularly polarized laser pulses at intensities of 1020 W/cm2. Physics of Plasmas, 18(4):. doi:10.1063/1.3577573.