Via LLRX – 2020 Open Educational Resources (OER) Sources and Tools – This is a comprehensive listing of Open Educational Resources (OER) sources and tools available in the United States and around the world, by Marcus P. Zillman. His guide includes references to: search engines, directories, initiatives, books, E-books, E-textbooks, free online seminars and webinars, subject guides, open and distance learning, open access papers and research, as well as related costs and metrics to identify and choose reliable, subject matter expert sources for free and open continuing education and research on the internet.