I received an honorary doctorate for my work. Maybe one of these works is considered the equivalent of a Ph.D.
It's much more difficult to work on a broad subject than on a specific one, because even if it's hard to find the information, if you look hard enough for something specific you will find it, and you will discover things that you wouldn't have thought of before.
When you take something extremely broad, then it is not a work of expansion or work of compression. It's hard because you have to decide what to throw out.