OPENGL bitmap & stroke text
http://dis.dankook.ac.kr/lectures/cg07/entry/OPENGL-bitmap-stroke-text
Sierpinski gasket
http://dis.dankook.ac.kr/lectures/cg07/entry/시어핀스키-가스켓Sierpinski-gasket
OPENGL geometry primitives
http://dis.dankook.ac.kr/lectures/cg08/entry/OPENGL-geometry-primitives