That great humorist and learning fair "macha" Sam Zilberzweig once asked a befuddled waiter what his favorite sauce was. The waiter said tomato sauce, to which Sam replied, "Well, mine is primary source." I can just see a reader's reaction. I've seen it before on the face of many of my colleagues when told a Sam joke. The picture above shows a portion of the 1880 census for 79 Clinton Street. Notice "Ma" is probably at some other hideout.
Here's the full census page and an integrated assignment for that page.