Articles owned by the university
Cost of Material: Free
Articles are available free of cost to students through the library’s online databases.
I have used a short book I put together from wikisource, and I use articles sometimes that I download and put into PDF format. I've also used PDFs of journal articles or other historical papers. Sources I've used include Social Science Research Network, Wikisource, the Cato Institute, the Mercatus Center, government websites for data and policy papers, and I'm sure several others, too. I also search for low cost sources and references to teach students from, for example the Critical Thinking Institute.