Reiner Creutzburg Valeri G. Labunets Ekaterina V. Labunets Towards an "Erlangen Program" for General Linear Systems Theory. 32-51 1991 conf/eurocast/1991 EUROCAST db/conf/eurocast/eurocast1991.html#CreutzburgLL91 http://dx.doi.org/10.1007/BFb0021003