Copyright © 2017 by Rafael Capurro, all rights reserved. This text
may be used and shared in accordance with the fair-use provisions of
U.S. and international copyright law, and it may be archived and
redistributed in electronic form, provided that the author is notified
and no fee is charged for access. Archiving, redistribution, or
republication of this text on other terms, in any medium, requires the
consent of the author.