The first boundary value problem for certain linear elliptic differential equations involving two small parameters

Asymptotic solutions of singular perturbation problems for linear differential equations of elliptic type

1966 • 154 citations

The First Boundary Value Problem for εΔu + A(x, y)u x + B(x, y)u y + C(x, y)u = D(x, y) for Small ε

1950 • 98 citations

Singular perturbations of boundary value problems for linear ordinary differential equations involving two parameters

1967 • 38 citations

On a class of singular perturbation problems

1964 • 22 citations