Kelter, M. [P:(DE-Juel1)145869] ; Huisman, J. A. [P:(DE-Juel1)129472] ; Zimmermann, Egon [P:(DE-Juel1)133962] ; Kemna, A. [P:(DE-HGF)0] ; Vereecken, H. [P:(DE-Juel1)129549]