This guide contains sources that could be used for content analysis. For particular titles of newspapers and magazines, it is best to check beforehand about years of coverage available before proceeding with a project.
Many source archives are listed in the Databases A-Z.
This link allows one to search for magazines, newspapers and journals by title. Many newspaper and magazine titles can be found in different places. Formats can also differ; some are text only, some are digitized images of the original print.