2Sirtori S, Maier G, Novati G, et al. A Galerkin symmetric boundary element method in elasticity formulation and hnplernentafion. Int J Nine Meth Eng, 1992, 35:255-282.
3Layton J B, Ganguly S, Balakrishna C, Kane J H A symmetric Cralerlon multi-zone boundary element formulation. Int J Num Meth Eng, 1997, 40:2913-2931.
4Gray L J, Paulmo G H. Symmetric Galerkin boundary integral formulation for interface and multi-zone problems. Int J Num Meth. Eng, 1997, 40:3085-3101.