The term "orphan work" is used to describe a situation where it is difficult or impossible to contact the copyright holder of a copyrighted work. This situation can arise for many reasons. The author could have never been publicly known because the work was published anonymously or the work may have never been published at all. Even if the author is known, the copyright may have been transferred to a relative, estate, or publisher. Nearly any work where a reasonable effort to locate the current copyright owner fails can be considered orphaned.
Should you use an orphaned work? Quite simply, you should balance your need against the potential risk of being sued by an unidentified rights holder. In addition, before using the work you might also consider these alternatives:
Consider the "potential market" for the work in question, and the possible harm to that market caused by your use of the work. If you discover that there is no way to acquire the proper permissions, you should reevaluate the fourth factor in the fair use analysis. You may find that this factor now weighs in favor of fair use. For more information, see Fair Use.
Can you locate a similar source with an identifiable copyright holder? If so then contact that rights holder and seek out the appropriate permissions. Or, you might also be able to locate an equivalent source that is in the public domain.
Rethink Your Intended Use
Rather than use the entire work can you cite a small portion of the work or even paraphrase relevant points? Relying on quotations, paraphrasing, and proper citation methods can often help you avoid the copyright permissions process altogether.
Some Suggested Resources