Mehler, M. J.: 'Electromagnetic wave propagation' (Electromagnetic Waves, 2003), 'Propagation of Radiowaves', 2nd ed., Chap. 5, pp. 75-86, DOI: 10.1049/PBEW502E_ch5 IET Digital Library, https://digital-library.theiet.org/;jsessionid=59mcagjqi9h7v.x-iet-live-01content/books/10.1049/pbew502e_ch5