"3) the amount and substantiality of the portion used in relation to the copyrighted work as a whole..."
It is fair use to properly quote from a source, that would be taking a portion. However, when an entire article is copied---"work as a whole," that leans more toward unfair use even though the user is a nonprofit or uses the material for educational purposes. Of course it also depends upon the copyright holder's grant of permission which makes it critical to check the grant of rights that each site lists to make sure your use does not infringe.
The reality is that there is no "one size fits all" in this area. The safest thing to do is as suggested and provide the link to the information or provide the address where interested parties can retrieve it from the source.
Peace
---
The Museum-L FAQ file is located at http://www.finalchapter.com/museum-l-faq/ . You may obtain detailed information about the listserv commands by sending a one line e-mail message to [log in to unmask] . The body of the message should read "help" (without the quotes).
If you decide to leave Museum-L, please send a one line e-mail message to [log in to unmask] . The body of the message should read "Signoff Museum-L" (without the quotes).