In his directives to all regional party officials (Kreisleiter) on July 7, 1933, the Party chief of propaganda (Gaupropagandaleiter der NSDAP) in the Koblenz Trier district called for a struggle against the Jews.
...The regional administration shall appoint a committee to manage and oversee all localities in the region.... The committee shall establish local committees, the names of whose members shall be known only to the regional committee. The members of the local committees shall forward to the regional committee the names of all Party members and other Germans especially civil servants who buy from Jews. The regional committee will produce, in duplicate, letters warning members of our people of the damaging effects of their behavior and calling their attention to the magnitude of the disgrace that will befall them if their actions become widely known. The letters will be phrased in such a way as to indicate only the address of the addressee, the shop, and the date and time of the purchase. The letters will be unsigned and will be sent from different post offices
For reasons of national interest, Party members must stop consorting even with their best friends if these people continue to buy from Jews. It should be stressed that the goal is that no German will speak with a Jew except where this is unavoidable.
For the time being, German girls who continue to consort with Jews should be warned of the danger of their behavior. In any case, members of our organization must have no relationship with such a girl.
Source: The Trial Against Major War Criminals, International Military Tribunal, Vol. XXV, Nuremberg, 1947/8 p. 379.