Time: From Earth Rotation to Atomic Physics - Dennis D. McCarthy, Kenneth P. Seidelmann - Google Books

https://books.google.de/books?id=7NdrK4e77CIC&pg=PA17&dq=%22Greenwich+Mean+Time%22+OR+GMT#v=onepage

Filling the need for a book that conveys the current technology as well as the underlying history and physical background, this book tells physicists and engineers how to measure time to the precision required for modern-day use. The authors draw on their…