Three whites sentenced to prison for burning a cross on a black family's lawn have been ordered to study black history while behind bars.

The defendants - two women and one man - expressed regret for the pre-dawn cross burning at their sentencing in federal court Friday, but U.S. District Judge Anne Thompson told the three they have more to learn.Thompson ordered the three to view a television documentary on the civil rights movement, "Eyes on the Prize;" read the book on which the series was based; and write a 25-page report on what they learned plus 10-page biographies on famous blacks.

After they finish prison terms ranging from nine to 13 months, the defendants will also have to perform 100 to 150 hours of community service in urban neighborhoods.

"Ultimately, the court must balance its consideration of the people who suffered a terror they did not deserve," Thompson told defendant Lisa Pfettscher. "They were as entitled to improve their life as you."

Pfettscher, 27, admitted she organized last September's cross burning because she feared property values would fall if more black families moved into her Camden, N.J., neighborhood.

Pfettscher and a friend, Theresa Kling, 32, paid Gary Lewis Ragan $75 to burn a cross on the lawn of Pfettscher's next-door neighbor, Paulette McCormick, who lives there with her two children.

No one was injured.

Pfettscher said she "had made a stupid mistake, not because I hate blacks or even had any problem with them but because I had set my goals. "