In addition to all submissions here. Either you are physically present or you book online. You have to book ahead your visit.
Website si.edu
Http://nmaahc.si.edu, click "Passes" or you can just walk up for the 1:00 PM weekday handout passes
Go to their website...I've forgotten. But do a search and it'll guide you.
Go to their website for all the info about tickets
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