Registration with the Copyright Office is not required in order for a work to be protected under U.S. copyright law. Works in the public domain, such as works created by the U.S. government, may be freely copied. The absence of notice cannot be relied upon to indicate that a work is in the public domain. Similarly, the fact that the author is deceased or the book is out of print does not mean that the work may be copied. Fair use does not apply to copied material which is sold to students.
Most publishers charge royalties.
The average royalty is 5 cents per page, per copy, but can often be much higher. Response time from publishers varies and can take up to 6-8 weeks in some cases, or can be denied. For further information you can visit Questions and Answers on Copyright for the Campus Community . It also includes information on software and other internet issues. A well prepared bibliography is essential.