8Xu Dan, Tang Yingping. Two-dimensional teaching in 3-D mechanical drawing [C]//The l lth International Conference on Geometry and Graphics, i-5, Guangzhou, China(9pt), 2004: 247-250.
10Xu Dan,Tang Yingping.Two-dimensional teaching in 3-D mechanical drawing[C]//The llth International Conference on Geometry and Graphics,1-5,Guangzhou,China (9pt),2004:247-250.