copyright infringement

"Fair use" is a defense to a charge of copyright infringement. It relies on 4 factors, including 1 the purpose and character of your use 2) the nature of the copyrighted work 3) the amount and substantiality of the portion taken, and 4) the effect of the use upon the potential market.

If you're providing a footnote, it sounds like your work and the original work are non-fiction, but you haven't provided enough information here to provide much of an answer - is your book a textbook, for educational use, or is it fiction? Are you copying 3/4 of the article in the beginning of your book, or 1 paragraph of a 20 page work on p. 200? Is you book on the same subject aimed toward the same market as the article's?

Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.

The information at the link below may help you figure out whether your use of another author's text constitutes fair use.

Disclaimer: This post does not constitute legal advice and does not establish an attorney-client relationship.