To find primary sources, try limiting by date or, under format, you can choose the "archival material" link. Then, use the "Request Item" button. Note that rare materials may be unavailable for loan.
Request items not owned by Helmke Library. This free service is an easy way to access almost any published book or article of interest. This will take approximately 1-2 days for digital items and 1-2 weeks for physical media.