1. Die Kombination des modifizierten Trefftzschen Verfahrens mit der Methode der Finiten Elemente;Stein,1973
2. Theory of connectivity for formall symmetric operators;Herrera,1977
3. Connectivity as an alternative to boundary integral equations: Constructions of bases;Herrera,1978
4. Boundary methods; a criterion for completness;Herrera,1980