Vortex clustering: The origin of the second peak in the magnetisation loops of type-two superconductorsD. K. Jackson, M. Nicodemi, G. K. Perkins, N. A. Lindop and H. Jeldtoft JensenEurophys. Lett., 52 2 (2000) 210-216DOI: https://doi.org/10.1209/epl/i2000-00425-9