Final answer:
Source documentation for study data can be maintained in both Electronic Health Records (EHR) and paper-based files at VHA medical centers.
Step-by-step explanation:
At VHA medical centers, source documentation for study data can be maintained in both Electronic Health Records (EHR) and paper-based files. Electronic Health Records (EHR) are digital records that contain patient information and can be accessed and shared among health providers. Paper-based files, on the other hand, are physical documents that are stored and maintained in a traditional paper format.