OR ---Real expertize to enable design/trouble-shoot complex systems?
And again- what DO you mean by"hydrulics"?
Oil Hydraulics Systems in Machine Tools,Robotics OR
Irrigation/Dams/Flow of Oils/water--pumps,turbines
In the 15th Century Leonardo da Vinci studied questions of hydraulic engineering.
In his Paper on the Flow of Water and River Structures he set forth his observations and experience gained in the construction of hydraulic installations in Milan, Florence and other places....
If you have BSc level math background you can walk into any decent book store & pick up any American fluid mechanics text book & teach yourself.
I recommend American because those are the only ones that explain everything in full detail without skipping any step. And I mean original US published books not the Indian editions. Quality of paper & printing can turn you off from learning the subject. Indian text books are notorious in that regard. I am speaking from 1st hand experience.