说明：  南京航空航天大学的CAD制图教程，很适用，对新手来说它有许多方面的优点，使新手很容易掌握CAD制图的fangfa
(Nanjing University of Aeronautics and Astronautics of the CAD drawing tutorial, it is applicable, on the green hand for it has lot of advantages, so that novices can easily master the CAD drawing fangfa)