6Chen Renzhao, Zhang Zhiyue. On penalty shifting method for distributed parameter systems on double connected region[J]. Proceeding of Systems Science Systems Engineering. Great Wall(H. K)Culture Publish Co, 1991. 170- 184.
7Dipllo G, Grippo L. On the method multipliers for a class of distributed parameter systems. IFAC 2nd Sysposium on Control of Distributed Parameter Systems. 28 June-1 July 1977, Uninversity of Warwick Coventry England. Section 3. Numerical Techniques.
8Lions J L. Operational Differential Equation and Boundary Value Problems[M]. Berl-in: Springer-Verlag, 1970. 60-61.