recently acquired
1967-04-08-Walker Art Center-Minneapolis-USA
1967-12-02-Stanford Art Gallery-Stanford-USA
2019-05-25 - Kunsthaus NRW Kornelimünster - Aix-la-Chapelle - Germany
1968-Wallraf Richartz Museum-Cologne-Germany
1969-01-19-Ucla Art Galleries-Los Angeles-USA
1969-05-17-Howard Wise Gallery-New York-USA
1969-08-17-Schleswig-Holsteinisches Landesmuseum-Schloss Gottorf-Schleswig-Germany-a
1969-09-10-The Detroit Institute of Arts-Detroit-USA-a
1969-09-10-The Detroit Institute of Arts-Detroit-USA-b
1970-01-21-Rose Art Museum-Waltham-USA
1970-03-19-Kunstverein Hannover-Hannover-Germany
1970-06-11 Kölnischer Kunstverein - Cologne - Germany
1970-09-25-Hayward Gallery-London-Great Britain
1970-11-06-Kölnischer Kunstverein-Cologne-Germany
1971-05-16-Heidelberger Kunstverein-Heidelberg-Germany
1971-06-19-Park Sonsbeek-Arnhem-Netherlands
1971-06-19-Park Sonsbeek-Arnhem-Netherlands-a
1971-11-Sonsbeek-Netherlands-a
1971-11-Sonsbeek-Netherlands-b
1971-11-Sonsbeek-Netherlands-c
1973-02-15-Kunsthistorisch Intituut-Amsterdam-Netherlands
1973-10-06-künstlerhaus-Graz-Austria
1973-10-27-Moderna Museet-Stockholm-Sweden
1974-01-19 - Kunsthalle Bern - Bern - Suisse a
1974-01-19 - Kunsthalle Bern - Bern - Suisse b
1974-07-06-Cologne-Germany
1974-07-06-Kölnischer Kunstverein-Cologne-Germany
1974-09-14-René Block Gallery Ltd.-New York-USA
1974-11-08-Musée d´Art Moderne de la Ville de Paris-Paris-France
1975-01-17-Institute of Contemporary Art University of Pennsylvania-Philadelphia-USA
1975-04-Fundacion Museo de Arte Contemporaneo de Caracas-Caracas-Venezuela
1975-05-25-Galleria Civica d´Arte Moderna Palazzo dei Diamanti-Ferrara-Italy
1975-06-08-Long Beach Museum of Art-Long Beach-USA
1975-09-15-La Biennale di Venezia-Venice-Italy
1975-09-30-University of California at Santa Barbara Art Galleries-Santa Barbara-USA
1975-10-14-Wright State University Art Gallery-Dayton-USA
1975-10-17-Städtische Kunsthalle Düsseldorf-Dusseldorf-Germany
1976-02-08-Kunst-und Museumsverein Wuppertal-Wuppertal-Germany
1976-09-05-Akademie der Künste-Berlin-Germany
1976-06-09-The Institute for Art and Urban Resources Inc.-New York-USA
1976-10-20-Städtische Kunsthalle Düsseldorf-Dusseldorf-Germany
1977-05-20-Neuer Berliner Kunstverein e.V.-Berlin-Germany
1977-06-24-documenta 6-Kassel-Germany
1977-09-Continental Gallery-Lima-Peru
1978-09-21-Bonner Kunstverein-Bonn-Germany
1979-02-14-Kunst und Museumsverein Wuppertal-Wuppertal-Germany
1979-02-14-Kunst- und Museumsverein Wuppertal-Wuppertal-Germany
1979-06-15-Bonner Kunstverein-Bonn-Germany
1979-09-01-Everson Museum of Art-Syracuse N.Y.-USA-a
1979-09-01-Everson Museum of Art-Syracuse N.Y.-USA-b
1979-10-28-Museum Folkwang Essen-Essen-Germany
1979-11-09-Museum Boymans-van Beuningen-Rotterdam-Netherlands
1980-01-20-Akademie der Künste-Berlin-Germany
1980-03-12-DAAD Galerie-Berlin-Germany
1980-03-18-Kölnischer Kunstverein-Cologne-Germany
1980-04-03-Akademie der Künste-Berlin-Germany