Determining whether a given source is primary or secondary can be difficult sometimes. And, just to make things more confusing, in a few cases a source can be both!
Consult the Library Guide, Primary or Secondary?, listed on the Get Help page to help you decide.
Also check out this blog post from the Library’s Archives and Special Collections about the Odlin Letter, a source that is both primary and secondary.
If you need more help, ask us!