ABSTRACT
The solutions we obtained in sec. 2.5 for the Helmholtz equation () ∇ 2 u ( r → ) + k 2 u ( r → ) = 0 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429499012/e8c92c35-b767-46c7-a521-be53a7b0eaae/content/eq886.tif"/>
