To quickly locate a particular type of primary source in most online catalogues use the following terms as SUBJECT rather than KEYWORD terms:
Entries for countries and regions are usually subdivided by century. If you are looking for what is available to document general social or intellectual trends in a period search for the country's formal name (Great Britain, not "England") followed by the century designation: Great Britain 15th century. Major events in any century will often have a subheading of their own: Great Britain World War 1914 - 1918.
You can use the subheading Sources with these time period designations as well: Hundred Years War 1339 1453 Sources
When searching in WorldCat your result list will have a set of tabs at the top, two may be of interest for primary sources:
Primary source: In scholarship, a document or record containing firsthand information or original data on a topic. Primary sources include original manuscripts, articles reporting original research or thought, diaries, memoirs, letters, journals, photographs, drawings, posters, film footage, sheet music, songs, interviews, government documents, public records, eyewitness accounts, newspaper clippings, etc. Glossary of Library and Research Terms.
A book which is the edited text of a manuscript, diary, or other type of primary source is also a primary source. Thus, the printed editions of The Parliament rolls of medieval England 1275 - 1504 is also a primary source even though it was published in 2005.