Fair Use Doctrine
The “fair use” doctrine is an exception to copyright protection designed to encourage the free flow of ideas. Fair use allows you to use a small portion of a copyrighted work for certain purposes such as education, news reporting, scholarly research, commentary and parody. The legal standard is ambiguous, however – in the event of litigation, a court will determine whether your use was "fair" or not by weighing four factors: the purpose and character of your use, the proportion of the entire work that you used and its importance in the context of the overall work, the effect of your use on the market value of the work, and whether or not your use was for commercial purposes. The fact that you used a portion of a copyrighted work for commercial purposes by selling it does not necessarily mean that your use was an infringement but it does make a finding of infringement more likely. Your use is certainly not "fair" if you use all of a particular copyrighted work.
First Sale Doctrine
The “first sale” doctrine is an exception to copyright protection that allows you to sell a second-hand copy of a copyrighted work without paying royalties to the author or receiving permission to sell it. An example of a sale protected by the first sale doctrine is the sale of a second-hand print copy of a book. Sale of an e-copy of the same book would not be excused by the first sale doctrine because the sale of an e-copy requires producing a new copy.
If your intended use of copyrighted material does not fall within an exception to copyright protection, consider asking the author for permission to use his work. If the work includes a copyright notice, the name of the copyright holder at the time the work was published will be included. If not, you can navigate to the Copyright Clearance Center website and search for the work by title. If it is registered, its listing will include details on how to contact the copyright holder. You may then negotiate with the copyright holder for the right to use the work. If you are selling the work, or selling a work that incorporates copyrighted material, it is likely that the copyright holder will require a flat fee or a percentage of sales in exchange for granting you the right to use the work. You will also probably be required to list the author's name on all published copies.
Just because a copyrighted work was created and published abroad rather than in the U.S. does not mean that it is in the public domain in the U.S. Likewise, a work created and published only in the U.S. is not necessarily in the public domain abroad. Most of the world's nations are signatories to the Berne Convention for the Protection of Literary and Artistic Works, which extends reciprocal copyright protection among all member nations. Even nations that are not signatory to the Berne Convention may be signatory to another copyright convention, such as the Universal Copyright Convention, which offers essentially the same protection to copyright holders.