Dembowski, C.Gräf, H.-D.Harney, H. L.Heine, A.Heiss, W. D.Rehfeld, H.Richter, A.2004-12-102004-12-1020012001http://hdl.handle.net/2003/1821710.17877/DE290R-12147enThe American Physical SocietyPhysical Review Letters530Experimental Observation of the Topological Structure of Exceptional Points10.1103/PhysRevLett.86.787article (journal)