Dienstfrey, A.
, Hang, F.
and Huang, J.
(2001),
Lattice Sums and the Two-dimensional, Periodic Green s Function for the Helmholtz Equation, Proceedings of the Royal Society A-Mathematical Physical and Engineering Sciences, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=901516
(Accessed March 5, 2025)