Stone steles from the Cao Wei period of the Three Kingdoms (starting 241 AD), carved with the "Book of Documents", "Spring and Autumn Annals", and the "Zuo Zhuan" using three script styles: ancient script, small seal script, and clerical script. Also known as the [[正始石经|正始石經|zheng4 shi3 shi2 jing1]] or [[魏石经|魏石經|wei4 shi2 jing1]].

a problem in physics and celestial mechanics that involves calculating the motion of three point masses based on their mutual gravitational attraction

trisomy 21, a genetic disorder caused by the presence of all or part of a third copy of chromosome 21