@book{ 0-1153291541, title = {Paul Klee und seine Malerfreunde: Die Sammlung Felix Klee; 25. Mai bis 22. August 1971, Wilhelm-Lehmbruck-Museum der Stadt Duisburg}, author = {Klee, Paul and Klee, Felix}, editor = {Klee, Paul}, editor = {Klee, Felix}, address = {Duisburg}, publisher = {}, year = {1971}, language = {German}, url = {https://katalog.ub.uni-leipzig.de/Record/0-1153291541} }