1. Forsythe, G., Wasow, W.: Finite-difference methods for partial differential equations. New York: Wiley 1960.
2. Jamet, P.: Numerical methods and existence theorems of singular linear boundary-value problems. Doctoral Thesis, University of Wisconsin 1967.
3. —— Numerical methods and existence theorems for parabolic differential equations whose coefficients are singular on the boundary. Maths. of Comp.22, 104, 721–743 (1968).
4. —— Parter, S. V.: Numerical methods for elliptic differential equations whose coefficients are singular on a portion of the boundary. SIAM Journal, Series B4, 131–146 (1967).
5. Parter, S. V.: Numerical methods for generalized axially symmetric potentials. SIAM Journal, Series B2, 500–516 (1965)