1) 미분기하란 무엇인가? http://mathparadigm.blogspot.com/2007/04/manifold.html∞
- "리만 메니폴드"를 궁금해 하다가....

2) Round()
#define ROUND(x) x >= 0 ? (int)(x+0.5) : (int)(x-0.5)

3) 백만분의 1초 측정
timecalculation