Ohira, Takashi: 'Circuit theory on wireless couplers' (Energy Engineering, 2018), 'Wireless Power Transfer: Theory, technology, and applications', Chap. 5, pp. 65-82, DOI: 10.1049/PBPO112E_ch5 IET Digital Library, https://digital-library.theiet.org/;jsessionid=148oku0rd2d11.x-iet-live-01content/books/10.1049/pbpo112e_ch5