B. A. Thango, J. A. Jordaan, and A. F. Nnachi "Assessment of Transformer Cellulose Insulation Life Expectancy Based on Oil Furan Analysis (Case Study: South African Transformers)", Advances in Science, Technology and Engineering Systems Journal, vol. 6, no. 6, pp. 29–33, 2021, doi: 10.25046/aj060605.