Asiapac Editorial. (2004). . Translated by Yang Liping and Y.N. Han. Singapore: Asiapac Books Pte. Ltd. ISBN 981-229-376-0. Engelfriet, Peter M. (1998). . Leiden: Koninklijke Brill. ISBN 90-04-10944-7. Ho, Peng Yoke. (2000). . Mineola: Dover Publications. ISBN 0-486-41445-0. Needham, Joseph (1986). . Taipei: Caves Books, Ltd. Restivo, Sal. (1992). . Dordrecht: Kluwer Academic Publishers. ISBN 1-4020-0039-1. O'Connor, J. J., and E. F. Robertson. "Guo Shoujing." School of Mathematics and Statistics. Dec. 2003. University of St. Andrews, Scotland. 7 Dec. 2008 <http://www-history.mcs.st-andrews.ac.uk/Biographies/Guo_Shoujing.html>. "China." Encyclopædia Britannica. 2008. Encyclopædia Britannica Online School Edition. 24 Nov. 2008 <http://school.eb.com/eb/article-71727>. Kleeman, Terry, and Tracy Barrett, eds. The Ancient Chinese World. New York, NY: Oxford UP, Incorporated, 2005. Shea, Marilyn. "Guo Shoujing - 郭守敬." China Experience. May 2007. University of Maine at Farmington. 15 Nov. 2008 <http://hua.umf.maine.edu/China/astronomy/tianpage/0018Guo_Shoujing6603w.html >. "China." Encyclopædia Britannica. 2008. Encyclopædia Britannica Online School Edition. 24 Nov. 2008 <http://school.eb.com/eb/article-71735>.