A Swiss museum said it would give up almost 40 works of art after a years-long investigation concluded they were either stolen by the Nazis or of doubtful origin. But the Museum of Fine Arts Bern said almost 1,100 other works from the same trove would be retained despite their provenance remaining unproven. German-Austrian collector Cornelius Gurlitt died in 2014 and left more than 1,600 works to the museum, including paintings by Pierre-Auguste Renoir, Paul Cezanne, Max Beckmann, Eugene Delacroix and Edvard Munch. Gurlitt's father was one of four art dealers tasked by the Nazis with selling art stolen from...