Some older articles might be available only on microfilm/microfiche, physical formats similar to slides or rolls of old-school camera film! You have 2 options for viewing them:
If you're already followed the suggestion on the Named Reactions tab, you should have the citation for the original article where your named reaction was published. Now you need to find that article! If you're lucky, it will be linked from the Wikipedia article on your named reaction (if there is one). If not, try some of the methods suggested below to find the original article.
Need help? Contact your librarian!
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