Matsuki, Hidetoshi: 'Basic theory of inductive coupling' (Energy Engineering, 2018), 'Wireless Power Transfer: Theory, technology, and applications', Chap. 2, pp. 7-22, DOI: 10.1049/PBPO112E_ch2
IET Digital Library, https://digital-library.theiet.org/;jsessionid=9etgact7l2det.x-iet-live-01content/books/10.1049/pbpo112e_ch2