I maintain an archive of pages that I link to in my posts in the /archive and /public/archive directories on this website (see the page source code). The web changes all the time and there is no way to be sure that content I once linked to will remain accessible in the future. To protect against this, I download copies of most pages that I link to and save them in /archive (HTML) and /public/archive (PDFs, images, etc.). This way, I can be confident that future readers of my blog will have access to all relevant information. The archive will only disappear when the rest of my blog does.
DISCLAIMER: All archived materials were created by their respective authors and are subject to their original licenses and terms. If you are the copyright holder of any content and would like it removed, please contact me.