Evaluation of data completeness in the electronic health record for the purpose of patient recruitment into clinical trials: a retrospective analysis of element presence - Köpcke, F; Trinczek, B; Majeed, RW; Schreiweis, B; Wenk, J; Leusch, T; Ganslandt, T; Ohmann, C; Bergh, B; Röhrig, R; Dugas, M; Prokosch, HU (BMC Med Inform Decis Mak, 2013)