Unusual quasars from the Sloan Digital Sky Survey selected by means of Kohonen self-organising maps H. Meusinger, P. Schalldach, R.-D. Scholz, A. in der Au, M. Newholm, A. de Hoon and B. Kaminsky A&A, 541 (2012) A77 Published online: 01 May 2012 DOI: 10.1051/0004-6361/201118143