On this page, we present a few lists of websites where you can find open textbooks or open (access) journal articles, which you can use as reading materials in your classes. For those, most likely those in the Humanities & Arts, looking for older materials to use as reading materials, such as scans of old documents or public records, we recommend also looking at the page for the multimedia resources, as we have put websites hosting such resources (museums, public institutions) in those lists.

There are a number of points that may be relevant to you as you use this page to find relevant OER:

• There are multiple lists, as we have tried to split them by general subject areas, in order to simplify the searching process. However, It may be that books from different disciplines are found on websites listed as hosting books from another discipline, as the divisions are not perfect. If applicable, we have indicated more specific subject fields in the description of the source.
• These lists are generally ordered based on usability, breadth, and perceived quality of the listed website, with likely more useful websites being listed first. However, this ordering is subjective, and therefore may not align with your experience of the listed websites.
• Related, these lists are not compiled by subject experts in the specific field, the ordering cannot be used as indication of the quality of the specific OER found on these websites. We suggest using the evaluation criteria in our guide on searching for and evaluating OER to help you judge the quality of the OER found on or via these websites.
• It may be that some listed websites provide resources that are not open, but only free, or require further login to fully access the listed resource. As much as possible, we'll try to indicate the general license information for the resources on each website, but we strongly recommend closely examining the license for any resource that you may wish to start using.

If you have found an interesting website or resource on or via this list, and you want to know how you could start using it, the OER support services are here to help. You can reach us at: oer-library@rug.nl.

This list has websites that hosts open textbooks and journals from a variety of fields, with no field being the most prominent.

• Openstax - CC BY, with some exceptions - Reviewed, high quality textbooks that have already been often used in teaching across the globe
• Figshare - CC licenses - Research output in the broadest sense, but a lot of articles generally. You can filter for CC licensed content
• Preprint Archive Service - Depends on resource, check license section - A central hub where many of the preprint archives (arXivs) can be searched, created by the well known Open Science Framework
• Milne Open Textbooks - CC licenses - Textbooks by the State University of New York (SUNY) Geneseo publishing house. Easy searching and professional online look
• Pressbooks Directory - CC licenses and Public Domain - Huge selection of high quality open textbooks, presented in a polished and interactive environment
• OAPEN - Filterable by CC license - Big selection of Open Access books and chapters. By filtering the search you can prevent finding incomplete records
• Manitoba Open Textbooks - CC licenses, and no ND - Simple and clean website to search for open and editable books
• Open Textbook Library - CC (no ND) and GNU GPL - A famous search engine for open textbooks, with a review system to see how other educators use the books
• Libretexts - CC BY-NC-SA unless otherwise stated - A multi-layered library that funnels you to the right book for your course
• intechOpen Books - CC BY and CC BY-NC - High quality, peer-reviewed books on many subjects  

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• Bloomsbury Academic - CC licensed, though generally with ND - High quality open access publications from an established publisher
• Oregon State University Open Textbooks - CC licensed (no ND) - Smaller university press collection, but good licenses and nice presentation platform
• Unglue - Open license or Public Domain - Open books with clear license information. Website is a little slow and searching can be a bit tricky as you sometimes need to click on more filters to get to specific subject
• Digital Commons Network - Varied licenses - Search engine that indexes a lot of open resources through their network. Searching for specific outcomes can be though, but a good way to get an overview
• College of the Canyons - CC licenses - Small collection of Zero Cost Textbooks that have been used in class at the College of the Canyons

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• 2012 Book Archive - CC BY-NC-SA (but check attribution page) - A collection of books that have been "saved" under their original license when a publisher decided to remove it in 2013. Because of this, they can be a little outdated 
• Scielo Books - CC licenses - A collection of open access books from Latin America. An important place for those looking for a more international perspective
• University of Wisconsin-Madison Pressbooks - CC licenses - Small collection of University of Wisconson-Madison Press. Utilizes the interactivity of the Pressbooks platform
• Springer Open Books - CC licenses - Open Access collection of well known publisher Springer. Generally Research articles, but also quite some book chapters
• Textbook Equity - CC licenses - Good selection of books, but with a slightly dated look, and difficult to find license information for some titles
• Directory of Open Access Journals (DOAJ) - Open licenses, often CC - Well known search engine for Open Access Journals and Articles
• Public Library of Science (PLoS) - Open licenses, often CC - A collection of journals that publish open access, although there are some reputational issues regarding the review procedure at these journals
• Directory of Open Access Books (DOAB) - CC licenses - Well known repository for Open Access Books. Presented books are not always made with teaching in mind, and are often in non-editable pdf format  

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• Ubiquity Press - CC BY - 100% Open Access publisher with books in many fields. Website can sometimes time-out, and search function is a little limited
• Taylor Francis Open Ebooks - CC BY-NC-ND - Well known publisher with a large selection. Many books are however not directly useful for teaching, and the license is limiting
• Paperity - Open license, often CC - Powerful aggregator of Open Access journal articles. Huge collection can be a little overwhelming, and license information can be a bit hidden
• Wikibooks - GNU Free documentation or CC BY-SA - Wikipedia book collection that anyway can work on. Website is a wiki-based domain, so navigation can be a little challenging at times. Also contains a lot of unfinished works
• Project Gutenberg - Public Domain (US) - Well known website with open ebooks of classic tales and writing. Formatting is very basic, but allows for quite easy adapting. Website is a little dated in appearance
• CORE - Open licenses, generally CC - Aggregator of Open Access journal articles. Also sells services, which can get a little in the way when starting with the website
• Project Muse Open Access Collection - Open Access, but not all CC - Lots of books, but some are still copyright protected. Website can slow down from time to time
• Open Access Journals - Open Access - list of Open Access journals. No further curation in the list of the journals is present, so may be difficult to judge the value of each by this list alone, as you need to click on each resource. Also, large focus on research and publishing, not education
• Athabasca University Press - CC BY-NC-ND - Collection from Athabasca University press. Nice looking online reader and pdfs, but books are not necessarily created with teaching in mind, and license is restrictive

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• Cornell University Press Open Access - CC BY-NC-ND - Restrictive license, and no easy search option available with filters for open content
• Just Free Books - depends on resource, with sometimes information lacking - Search engine for free ebooks, but website has an unsecure connection and license information can be complicated
• University of Minnesota Publishing - CC licenses - Books, journals, and syllabi. Website is a little sparse, which can make searching a little bit of a hassle
• LiveCarta - Has CC licensed content - Shop, but with a few open options. The mixed nature can make it difficult to find all open materials, and thus those relevant

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• PDXScholar Open Textbooks - CC BY-NC - Small collection with okay license, but search function goes broader then just the listed books, making it difficult to get a good overview
• City University of New York Manifold - Mixed, also copyright protected materials - Collection of books with either very restrictive, or no open license, and no easy way of finding out quickly
• State University of New York Open Access Repository (SOAR) - Open Access, but specifics unclear- repository of books, but also academic works such as (student) theses. Licensing information can be unclear
• MIT Press Open Access Books - CC BY-NC-ND - Small collection of Open Access books, but with a restrictive license.
• DSpace by SUNY - seemingly CC BY-NC-ND - Collection of academic works with a restrictive license. License information can be difficult to find, and exact uses of materials can be unclear
• National Academies Press - Open Access, but not open - Free, but not openly licensed books and reports. Not a direct educational focus
• La Trobe eBureau Books - CC licensed - Small collection of books from a university press. License information is not directly clear 

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• University of North Dakota Scholarly Commons - Open Access - Collection of materials that range in quality and breadth, and unclear license information
• University of Minnesota Manifold press - Open Access - Mix of CC licensed and copyright protected publications from a university press. No clear way of directly finding the license information
• Simon Fraser University Publication Series - Open Access - Small collection from a university press. No clear license information on overview, and also contains copyrighted materials

This list has websites that hosts open textbooks and journals mainly from fields related to science, technology, engineering, math, and medicine. For instance, books on physics, mathematics, geography, computer science, and biology can be found here.

• Freetechbooks - Open licenses, generally CC - Books and lecture notes with clear licensing, easy searching and downloading
• Light and Matter - CC BY-SA - Small, but impressive collection of books on physics and STEM in general with clear license
• American Institute of Mathematics - CC licenses, but also some just free - Curated list of open books on mathematics, with links on where to find them 

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• OpenTextBookStore - CC licenses - Highly adoptable textbooks on mathematics with clear licenses and supplemental materials
• Open Geography - CC BY-NC-SA - Collection of geography eTextbooks published on Pressbooks
• NCBI Bookshelf - All Open Access, some CC licenses - Good search function, large collection, but quite US-focused
• EuropePMC - Open Access - Journal articles and preprints from the field of life sciences
• Green Tea Press - CC BY-NC(-SA) - Computer science and programming books, with supporting code on GitHub
• FreeComputerBooks - Licensing depends on the resource - Slightly dated website, but a large collection of computer science

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• TU Delft Open Textbooks - CC BY-NC-SA - Open textbooks with a focus on mostly STEM. Small collection, but clear information for each entry. Unfortunately not in editable format
• Biodiversity Heritage Library - Public Domain or CC BY-NC-SA - Books, journal articles and scanned texts from fields associated with biodiversity. Searching can be a bit difficult, as information is a little sparse, and website a bit busy
• EBook Foundation -CC BY - Large list of programming books in many languages
• Virginia Tech Open Textbooks - CC licenses - Small collection with open books on STEM. Amount of information can be a little overwhelming 

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• Motion Mountain - CC BY-NC-ND with restricted redistribution - One huge textbooks, but consisting of five volumes on physics and, specifically, motion. Very restrictive license unfortunately

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• Grand Valley State University Open Books - CC licenses - Small collection, but no easy search or license information. Books can also be found on other platforms
• FreeBooks4Doctors - Depends on resource - Search engine/list of books on medical topics, but website has unsafe connection, no clear license information or search, and can be difficult to navigate
• MedEdportal - CC licenses and Open Access - Journal articles for medical education. license information is not very clear, and website is quite text heavily, making navigation a challenge
• CK-12 - Free, but not open - Pre-university, US-based education website, that can be a little overwhelming and has no good open license

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• Aviation Handbooks and Manuals - Unclear, seems to be semi-public, may be Public Domain - Highly specialist manuals for planes, with no clear license information
• Teach Astronomy - unclear - Website that is quite buggy and dated, but has a lot of information astronomy. License information is lacking unfortunately

This list has websites that hosts open textbooks and journals mainly from fields related to arts, humanities and law. For instance, books on music, international relations, specific forms of law, and language can be found here.

• Pugetsound Music Theory - GNU Free Documentation License (CC BY-SA-esque) - Open (text)book and exercises on music theory. Website unfortunately has unsafe connection, but the material is detailed and has a good license
• Avalon Project - Free, likely Public Domain - Web versions of important historical, political, and law documents. License information is unfortunately missing, but due to age and type of documents is likely Public Domain
• E-international Relations Books - CC BY-NC - Impressive collection of international relations books with a good license, but lacking modifiable formats, and hosted on a website with some intrusive ads

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• Writing Spaces - CC BY-NC-SA - Collections of student and teacher essays on writing and style. Good license, but no modifiable formats, and niche topic
• American Yawp - CC BY-SA - A massive collaborative effort to chronicle the history of the United States (and earlier life on the North American continent). Also has an accompanying primary sources reader. Not a very editable format, but easy to copy and paste in loose documents
• Standard eBooks - CC0 - A website dedicated to make copyright-free texts, such as those found on Project Gutenberg, beautifully formatted and more accessible. Collection is mostly classic texts, in line with public domain basis of the website

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• University of Michigan Open Access Titles - CC BY-NC-ND - Large collection of Open Access titles on a good website, but with a restrictive license
• CALI e-books - CC licenses, mostly CC BY-NC-SA - Law books with a good license and editable formats. However, focus mostly on US law
• Open Square NYU press - CC BY-NC-ND/SA - Large collection, but not necessarily educational books, and newer books tend to have more restrictive licenses
• Humanities Common Core Open Access - CC licenses - Huge collection of Open Access articles. License info is clear on click-through, but no easy filters
• Open Book Publishers - CC licenses - Open (text)books with good licenses, but not always in modifiable format

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• H2O Open Casebook - CC BY-NC-SA - Website to create your own law textbook by combining case files. Unfortunately, relates to US law and need to sign-up in order to use
• Open Humanities Press - CC licenses - Books and journals in the humanities. License information can be difficult to find, and website has unsafe connection
• WAC Clearinghouse Open Access Textbooks - CC licenses - Small collection of resources for writing. License information is a little difficult to find, and website has a couple of dead links
• New Prairie Press - CC licenses - Small collection with limited scope from a university press. No online viewing unfortunately, which makes it difficult to evaluate materials quickly
• Fulcrum ACLS Humanities Ebooks - Open Access - Collection of mostly theology books. Unfortunately, license info is missing for some, and many others have restrictive ND license
• Edinburgh Open Books - CC BY, generally - Scans of prints and old books. Not very modifiable due to the nature of the materials
• Berghahn Open Access Books - CC BY-NC-ND - Large collection, but website has no easy search function, and books have restrictive licenses

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• Open Arizona - CC BY-NC-ND - Collection of a university press, but unfortunately with a restrictive license and not all books have a strong educational purpose

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• PSU Press Unlocked - Open Access - Open Access book collection from Penn State. Bit of hassle to get to the book and the license, with the link being hidden in a text book rather than a clear button. which leads to different sites
• Books@ATLA - Some CC, but also seemingly some copyrighted - Small collection, but unfortunately with unclear, mixed license information. No online viewer, or modifiable formats

This list has websites that hosts open textbooks and journals mainly from fields related to the social sciences and business. For instance, books on economics, psychology, education and pedagogy, and sociology can be found here.

• EconBiz - Open Access - Search engine for journals, working papers & conferences in Business & Economics. Useful for researchers and students
• Lyryx Open Textbooks - CC By or BY-NC-SA - High quality, peer reviewed books on business, economics and mathematics. Getting tot hem may require signing up, but the books can be found through other platforms such Open Textbook library
• NOBA Project - CC BY-NC-SA - 105 modules on different psychology topics that you can customize into your own textbook. Written by experts in the field, and with a permissive license. Do need to sign up and log in 

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• EdTechBooks - CC licenses - Collection of educational science books. You can search per license, but that limits the search results, and if you check all materials, you don't directly see the license, which can make searching a little awkward  

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• Open Social Work Education - CC licenses - Social work textbooks and Open Access books. Website lacks a dedicated search function or direct license information, but links through to all CC licensed content
• World Bank Group Open Knowledge Repository - Open Access (CC licenses) - Economics books and reports, but website can be alittle slow and license information is not directly apparent

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• CORE Econ - CC BY-NC-ND - Couple of ebooks on economics, but with a restrictive license, and many additional features being locked behind registration
• Rebus Community Open Textbook Directory - CC BY - Rebus Community's Pressbook page with interactive textbooks on open education and other topics