HHommage an das QuadratHommage an das Quadratde Marli Hoppe-Ritter, Gerda Ridler, Barbara WillertMateriasSquare in artExhibitionsArt collectionsModern ArtThemes, motivesMuseum Ritter (Waldenbuch, Germany)ArtSammlung Marli Hoppe-Ritter (Museum Ritter)Private collections