Morbidity and mortality of extremely low gestational age infants in Schleswig-Holstein. Follow-up at three to six years corrected age of infants < 27 + 0 weeks gestation in Schleswig-Holstein, Germany [in German] - Rapp, M; Thyen, U; Müller-Steinhardt, K; Kohl, M (Z Geburtshilfe Neonatol, 2005)