"Distribution Transformers: Basics, Maintenance, and Diagnostics" by M. Sidhu and H. Grady
"Transformers: Analysis, Design, and Measurement" by J. J. Winders Jr.
"Electric Power Distribution Engineering" by Turan Gonen
"Transformer Engineering: Design and Practice" by L. L. Grigsby
"Power Distribution Transformer Manual" published by IEEE
"Distribution System Modeling and Analysis" by W. Kersting
"Transformers and Inductors for Power Electronics: Theory, Design and Applications" by Marian K. Kazimierczuk and Dariusz Czarkowski
"Handbook of Transformer Design and Applications" edited by L. Demetriades
"Understanding and Applying the 2017 National Electrical Code Volume 2" by Mike Holt
"Transformer and Inductor Design Handbook" by Colonel Wm. T. McLyman
These books cover various aspects of distribution transformers including the design, operation, maintenance, diagnostics and related electrical codes and standards.