Li, C., Cen, S., XiangRong, F., Zhou, G., Zhou, M., & ChenFeng, L. (2011). Shape-free finite element method: The plane hybrid stress-function (HS-F) element method for anisotropic materials. Science China Physics, Mechanics and Astronomy, 54(4), pp. 653-665. doi:10.1007/s11433-011-4272-6

Li, Chenfeng, Song Cen, Fu XiangRong, GuoHua Zhou, MingJue Zhou, and Li ChenFeng. "Shape-free Finite Element Method: The Plane Hybrid Stress-function (HS-F) Element Method for Anisotropic Materials." Science China Physics, Mechanics and Astronomy 54, no. 4 (2011): 653-665.

Li, Chenfeng, et al. "Shape-free Finite Element Method: The Plane Hybrid Stress-function (HS-F) Element Method for Anisotropic Materials." Science China Physics, Mechanics and Astronomy 54.4 (2011): 653-665.