Reiner Creutzburg Valeri G. Labunets Ekaterina V. Labunets Towards an "Erlangen Program" for General Linear Systems Theory. 52-71 1993 conf/eurocast/1993 EUROCAST db/conf/eurocast/eurocast1993.html#CreutzburgLL93 http://dx.doi.org/10.1007/3-540-57601-0_40