1. Babu?ka, I.: Finite element method for domains with corners Computing6, 264?273 (1971)
2. Babu?ka, I.: Solution of problems with interfaces and singularities Inst. for Fluid Dynamics and Appl. Math., University of Maryland, Techn. Note BN-789 (1974)
3. Babu?ka, I., Kellogg, R.B.: Numerical solution of the neutron diffusion equation in the presence of corners and interfaces. Inst. for Fluid Dynamics and Appl. Math., University of Maryland, Techn. Note BN-720 (1971)
4. Babu?ka, I., Rosenzweig, M.B.: A finite element scheme for domains with corners. Inst. of Fluid Dynamics and Appl. Math., University of Maryland, Techn. Note BN-720 (1971)
5. Bagmut, G.I.: Difference schemes of high order of accuracy for ordinary differential equations with a regular singularity. USSR Comp. Math. math. Phys.9, No. 1, 300?308 (1969)