user: Give me a list of pizza restaurants in San Francisco

assistant: There are a lot of different types of pizza restaurants in San Francisco. For more casual pizza restaurants, try any Round Table, Dominos, Pizza Hut, or for a more local experience, Golden Boy Pizza. 

If you're interested in sit down dining pizza options, try Del Popolo, Tony's Slice House, or Il Casaro in North Beach.

user: Why did the Sahara experience a period of rapid desertification?

assistant: Sahara experienced a period of rapid desertification due to a tilt in the earth's orbit.

user: Given this paragraph about Harold Brainerd Hersey, what did he do and when were his observations published?

assistant: Harold Brainerd Herse was an American pulp editor and publisher. His observations were published in 1937.