Below is a list of free and reliable resources:
Copyright Term & the Public Domain in the United States
This chart illustrates when works pass into the public domain.
© Copyright Notice
Although works first published on or after March 1, 1989 are not required to bear a copyright notice, it is still advisable to include such notice on your work. A proper notice puts the public on notice that your work is protected by copyright so that potential infringers could not claim that they did not realize that the work was protected (i.e. the innocent infringement defense, which could reduce damages a copyright owner may recover).
Creative Commons Licenses
Traditionally, creators would reserve all rights in their copyrighted works. However, a Creative Commons license allows a creator to reserve some rights and communicate which rights they reserve and which rights they waive for the benefit of recipients or other creators.
Instead of transferring rights to publishers who restrict access to paid customers only, many authors choose to make their works freely available to all users with few or no restrictions on reuse. GT adopted an open access policy in 2013.
More Information on Fair Use
US Copyright Office elaborates on the four factors that guide fair use determination.
USG Board of Regents Fair Use Checklist
Should you need to make a fair use determination, the fair use checklist developed by the USG Board of Regents can help. The site also indicates that “complete and retain a copy of this checklist for each ‘fair use’ of a copyrighted work in order to establish a ‘reasonable and good faith’ attempt at applying fair use should any dispute regarding such use arise.”