Use, modification & distribution is subject to Boost Software License Ver 1.
http://www.boost.org/LICENSE_1_0.txt

Attributions:
The code in this library is an extension of Bala Vatti's clipping algorithm:
"A generic solution to polygon clipping"
Communications of the ACM, Vol 35, Issue 7 (July 1992) pp 56-63.
http://portal.acm.org/citation.cfm?id=129906

Computer graphics and geometric modeling: implementation and algorithms
By Max K. Agoston
Springer; 1 edition (January 4, 2005)
http://books.google.com/books?q=vatti+clipping+agoston

See also:
"Polygon Offsetting by Computing Winding Numbers"
Paper no. DETC2005-85513 pp. 565-575
ASME 2005 International Design Engineering Technical Conferences
and Computers and Information in Engineering Conference (IDETC/CIE2005)
September 24-28, 2005 , Long Beach, California, USA
http://www.me.berkeley.edu/~mcmains/pubs/DAC05OffsetPolygon.pdf