ABSTRACT
In the previous sections the approximate problems have been stated as operator equations on M. As in the application to second order problems (Sections 6 and 7) and to pseudodifferential operators (Section 8), the problems are presented as: Find U ∈ M such that A ( U , χ ) = F ( χ ) https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203746332/608738f3-7c7a-4b45-bdd9-ce6f43c0b870/content/eq998.tif"/>
