Includes links to copyright laws, websites and special topics that include information on using book covers on websites, fair use, public performance rights, and more.
(Image Source: https://pixabay.com/en/book-textbook-college-learning-845280/)
Permission trumps all. OFTEN if you take the time to write a quick email to a publisher with the passage copied, or referred to, they will grant you permission to use it. This is the best route. Find the "contact us" email address at the bottom of a publisher's website. If you have some favorite article you read, by all means contact the publisher. Carefully craft the wording to indicate you will not be posting this online.
Historical Primary Source texts are fair game and are likely archived via a government website. See some of the links below. Notice how some sites freely upload historical documents to their site. These are examples of fair use. They used them, so can you.
Two Great Resources from The Visual Communication Guy, http://thevisualcommunicationguy.com