Reasonably exhaustive reasearch

History researchers are trained not to make conclusions about issues until their research has been reasonably exhaustive. They comb the published literature and archival catalogs in search of relevant materials. If their subject is local or biographical in nature, they know that public records need to be explored. But no biography or local study can ever be complete until we have identified and studied the works of that area's unofficial record keepers. ... Oh? Who's that? ...