1. Song Qiu: The Foundation of Style Design (Tsinghua University Press, China 2005), p.155.
2. Lin Tao Tang: The Method of Industrial Design (China Building Press, China 2006), p.49.
3. Wu San Dai: Kao Gong Ji Said (Shandong Pictorial Publishing House, China 2003), p.89.
4. Yan Gao: The Materials of Industrial Design and Surface treatment (National Defence Industry Press , China 2005), p.22.
5. Nan Gao: The Method and Case of Innovation of Industrial Design (Chemical Industry Press , China 2004), p.125).