Star Trek: The Entropy Effect
by Vonda N. McIntyre
Spock and the rest of the crew of the Enterprise transport a time-traveling criminal, Dr.
Georges Mordreaux, between planets.
The effort required to change an event is proportional to the square of its distance in
the past. The curve of a power function approaches infinity rather quickly.
Star Trek: The Entropy Effect by Vonda N. McIntyre
(Pocket Books, June 1981).