The 'source' is years of study on WWII with a specific interest in the persecution of Jews in Germany.
On November 11th, 1938 (before the war) Germany passed "Regulations Against Jews' Possession of Weapons" (it's what they called it).
At that time Jews were wearing stars on their shirts, had been kicked out of a list of professions, but Ghettos were not yet there. The Jews that remained in Germany desperately worked to try to maintain a certain level of freedoms that they were doomed to lose over time, to do this they followed the laws in the hopes that "this one" would be the last. When the weapons ban came, almost all weapons were turned over pursuant to the law, and once the "Jewish Houses" were set up it became easier for the authorities to search and seize any weapons that remained.
After the war began (September 1st, 1939) more restrictions came on the Jews that were still in Germany, including restrictions of areas they could go, curfews, restrictions on the time of day they could purchase any food at all, food rationing specific to Jews, they passed regulations forcing Jews to turn over property (radios, electrical appliances, etc.), and forced labor for all Jews who were healthy enough to work.
While "ghettos" as we know them were never in Germany proper, restrictions on the areas they could live, forcing them to move into shared houses called "Judenhauser" or "Jew Houses", and curfew restrictions as well as restrictions to the time of day they could even purchase something, made effective ghettos.
