Abu Bakar, Norazhar: 'Power transformer asset management and remnant life' (Energy Engineering, 2018), 'Power Transformer Condition Monitoring and Diagnosis', Chap. 8, pp. 259-293, DOI: 10.1049/PBPO104E_ch8
IET Digital Library, https://digital-library.theiet.org/;jsessionid=4qk3m4s5fdnke.x-iet-live-01content/books/10.1049/pbpo104e_ch8