ABSTRACT
It is well known that in solving second order elliptic boundary value problems such as { − Δ u = λ u + f in Ω , u = 0 on ∂ Ω , https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003072195/76a9e30c-d2f5-45a2-8ce7-5dc6314e2d2a/content/eq1195.tif"/>
