After their experiences at the Eastern Front, having learned about mass murder in Poland and the Soviet Union, Hans Scholl and Alexander Schmorell felt compelled to take action. From end of June until mid of July 1942, they wrote the first four leaflets. Quoting extensively from the Bible, Aristotle and Novalis, as well as Goethe and Schiller, the iconic poets of German bourgeoisie, they appealed to what they considered the German intelligentsia, believing that these people would be easily convinced by the same arguments that also motivated the authors themselves. These leaflets were left in telephone books in public phone booths, mailed to professors and students, and taken by courier to other universities for distribution. From 23 July to 30 October 1942, Graf, Scholl and Schmorell served again at the Soviet front, and activities ceased until their return. In autumn 1942, Sophie Scholl discovered that her brother Hans was one of the authors of the pamphlets, and joined the group. Shortly after, Willi Graf, and by the end of December 1942, Kurt Huber became members of the White Rose.