Purple dwarfs: New L subdwarfs from UKIDSS and SDSSZ.H. Zhang, D.J. Pinfield, B. Burningham, H.R.A. Jones, A.C. Day-Jones, F. Marocco, J. Gomes and M.C. Galvez-OrtizEPJ Web of Conferences, 47 (2013) 06007DOI: https://doi.org/10.1051/epjconf/20134706007