' Woman Sitting in an Armchair ' was held by the now famous late artist . When he died a treasure trove of more than 1,500 works was uncovered . Latest to be returned belongs to heirs of art dealer Paul Rosenberg . Similar agreement was signed last night for auction by von Liebermann . Gurlitt 's father helped Nazis sell ' degenerate ' art outside Germany for sale .
'Woman Sitting in an Armchair ' was held by the now famous late collector . When he died a treasure trove of more than 1,500 works was uncovered . Latest to be returned belongs to descendants of art dealer Paul Rosenberg . Similar agreement was signed last week for painting by Max Liebermann . Gurlitt 's father helped Nazis sell 'degenerate ' art outside Germany for cash .