The concept of fair use deals with how much of a source you can borrow or quote. According to Section 107 of the Copyright Act of 1976 — the fair use provision (available at www.copyright.gov/title17/) — writers can use copyrighted materials for purposes of “criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research.” In other words, writers generally don’t need to seek permission to make brief quotations from a source or to summarize or paraphrase a source.

If you are working on an assignment for a course — and do not plan to publish the assignment on the Web or in print — you generally can use material from another source without seeking permission. Remember, however, that in all cases you must still cite the source of the material you use.

Writers who plan to publish their work — in a newspaper or magazine, in a blog, or on a public Web site, for example — should seek permission to use material from a source if they want to quote a lengthy passage or, in the case of shorter works such as poems and song lyrics, if they want to quote a significant percentage of the source. Writers who wish to use multimedia sources, such as images, audio, or video, should consider either seeking permission to use the source or linking directly to it. Be cautious, however, about linking directly to multimedia sources, since some Web sites specifically ask that you not link to content on their site (typically because doing so increases the demand on Web servers).

If you seek permission to use a source, explain why and how you want to use it. Many authors and publishers allow academic use of their work but frown on commercial uses. When you contact an author or a publisher, include your name and contact information, the source you wish to use, the purpose for which you will use the source, and the time during which it will be used.

If you contact an author or a publisher by mail, include a self-addressed, stamped envelope. It will save the recipient the cost of responding by mail, indicates that you are serious, and, perhaps most important, shows good manners.