[4] His dissertation was published by Gerd Hatje in the book, Sputnikschock und Mondlandung: Künstlerische Großprojekte von Yves Klein zu Christo (1989), and additional sections appeared in his catalogue, Walter de Maria: 5 Kontinente Skulptur (1989).
In 1988, Kellein was appointed Director of the Kunsthalle Basel, where he curated exhibitions of Mark Rothko, Clyfford Still, Andy Warhol, Roni Horn, Mike Kelley,[5] John McCracken, Cindy Sherman, Hiroshi Sugimoto, and Rachel Whiteread.
During his years in Basel, Kellein was guest curator at Watari-Um in Tokyo, at the Royal Academy of Arts in London and at Haus der Kunst in Munich.
With the help of the architectural firm Zwimpfer Partner, Kellein invited Donald Judd to Basel in 1991, where the sculptor developed the design of the façade of the Bahnhof Ost railroad station.
In Bielefeld he curated solo exhibitions by Alvar and Aino Alto, Vanessa Beecroft, Louise Bourgeois, George Condo, Paul Delvaux, Fang Lijun, Caspar David Friedrich, Adam Fuss, Donald Judd (which later travelled to the Menil Collection,[6] Ilya and Emilia Kabakov, Jeff Koons, Henri Laurens, Robert Longo, Kasimir Malevich, Yoko Ono, Pablo Picasso, Rirkit Tiravanija and Not Vital.
Among his thematic projects were “1937: Perfection and Destruction,” “1968: The Great Innocence,” and “The 80s Revisited: The Bischofberger Collection.” Many publications related to the listed exhibitions, including the ones in Basel, were issued by well-known German publishing houses.