Starting with version 1.2, Macaulay2 incorporates frobby, a free library of routines for computing the Alexander dual of a monomial ideal (see dual(MonomialIdeal), a method used internally by many routines), written by Bjarke Hammersholt Roune, and available at http://www.broune.com/frobby/. It is distributed under the terms of the GNU General Public License, version 2 (or later), see COPYING.