28th Automorphic Forms Workshop, Utah, United States Of America, 12 - 16 May 2014, pp.3
For describing automorphic forms of singular weight over number fields it is indispensable to understand the
representations of groups like SL(2,O), where O is the ring of integers of a number field. Even for SL(2,Z)
there are open questions. We report about recent progress on this problem for general arithmetic Dedekind
domains, and we discuss still open problems.