This work is licensed under a Creative Commons Attribution 4.0 International License. The problem appears in a list of puzzles maintained at [thinks_com].
The original website seems to have disappeared, but the referenced content is available at [thinks_com_wayback].
[thinks_com]
Crossfigure Math Puzzles
howpublished: http://thinks.com/crosswords/xfig.htm
[thinks_com_wayback]
Crossfigure Math Puzzles
howpublished: http://web.archive.org/web/20141017151205/http://thinks.com/crosswords/xfig.htm
This work is licensed under a Creative Commons Attribution 4.0 International License.