Other artists remained in internal exile. Otto Dix retreated to the countryside to paint unpeopled landscapes in a meticulous style that would not provoke the authorities. The Reichskulturkammer forbade artists such as Edgar Ende and Emil Nolde from purchasing painting materials. Those who remained in Germany were forbidden to work at universities and were subject to surprise raids by the Gestapo in order to ensure that they were not violating the ban on producing artwork; Nolde secretly carried on painting, but using only watercolors (so as not to be betrayed by the telltale odor of oil paint). Although officially no artists were put to death because of their work, those of Jewish descent who did not escape from Germany in time were sent to concentration camps. Others were murdered in the Action T4 (see, for example, Elfriede Lohse-Wächtler).