Patent Register

Sometimes you need to dig even further into a patent case. This is where the patent registers are necessary to access the complete file wrapper and history of a patent. Most patent offices provide access to these file wrappers. Here you can find all the correspondence between the owner ot the patent and the patent office including all documentation, amendments and arguments and get the complete picture of a case. 

Many of the major agencies (EPO, WIPO, USPTO, GTPO) provide online access to patent filing process data through the Patent Registry. In many cases, access to the patent files is also possible.
Links to the registers:
EPO (European Patent Office)
GPTO (German Patent and Trademark Office)
USPTO (US Patent and Trademark Office)
WIPO (World Intellectual Property Organization)