Original sentence: Gulbransson illustrated many books, including the children's books Det var en gang (Once upon a time), which was published simultaneously in Norway and Germany in 1934, and Und so weiter (And so on) which was published in Germany in 1954.In 1933 he already acted as signer of a petition against a Wagner-performance of Thomas Mann as "European" and "un-national".Nevertheless, Simplicissimus editors Franz Schoenberner and Thomas Theodor Heine have reasoned that Gulbransson actively cooperated with the nazis from 1933 onwards
Edited sentence: Gulbransson however remained a respected artist in Germany for the rest of his life.He illustrated many books, including the children's books Det var en gang (Once upon a time), which was published simultaneously in Norway and Germany in 1934, and Und so weiter (And so on) which was published in Germany in 1954