Lyalinov, Mikhail A.; Zhu, Ning Yan: 'Scattering of Wedges and Cones with Impedance Boundary Conditions' (Electromagnetic Waves, 2012) DOI: 
IET Digital Library, https://digital-library.theiet.org/;jsessionid=1vaok0qd68sj0.x-iet-live-01content/books/ew/sbew501e