Food and drink are permitted, but with some restrictions intended to protect books, computers, and other materials, and to maintain a comfortable and pleasant environment for all patrons.
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When you are choosing foods and drinks and containers, be considerate of other patrons (no strong-smelling foods) and sensible about the probability of spills and mess (no messy foods, put drinks in covered containers). Think of it this way: snacks yes, meals no.
And please clean up after yourselves. There are plenty of trash and recycling containers.