The common sense tells that the Doxygen comment blocks have to be put in the header files where the classes, structs, enums, functions, declarations are. I agree that this is a sound argument for a libraries that are mean to be distributed without its source (only headers and libs with object code).
BUT...I've been thinking of the exact opposite approach when I'm developing an internal to the company (or as a side project for myself) library that will be used with its full source code. What I propose is to put the large comment blocks in the implementations files (HPP, INL, CPP, etc) in order NOT to clutter the inteface of the classes and functions declared in the header.
Pros:
Cons:
So, what do you think and possibly suggest?