Stefan Tenbohlen, Maik Koch, Dejan Vukovic, Andreas Weinläder, J. Baum, Jörg Harthun, Michael Schäfer, S. Barker, Rainer Frotscher, D. Dohnal, and D. Dyer. Application of vegetable oil-based insulating fluids to hermetically sealed power transformers. 2008. [PUMA: Ageing Design Dielectric Ester Hermetical Natural OLTC Power Saturation Sealing Stability Strength Thermal Transformer Water] URL