Primary sources are generally considered to be firsthand accounts of an event or the actual documents associated with an event. Firsthand accounts can be found in diaries, memoirs, letters, speeches, autobiographies, scholarly articles giving the results of research, etc. Documents might be laws, treaties, transcripts of hearings, court cases, etc.
The word sources or documents or documentary usually occur on records for anthologies or collections of primary source material. Use those words in a keyword search to bring up collections of documents.
The library also has this series Sources And Documents In The History Of Art