The earliest finding aids were known as "calendars" and generally consisted of a listing of individual documents in chronological order, which was the preferred organizational method of historians, who were their primary users at the time. Currently used forms of finding aids vary in length and fall into several categories by type, with the inventory predominating in the late 20th and early 21st centuries.
The earliest reference tools were referred to as "calendars" and typically consisted of a listing of individual documents in chronological order, which was the preferred method of organization favored by historians, who were their primary users at that time. Currently used forms of reference aids vary in length and fall into several categories by type, with the inventory being predominant in the late 20th and early 21st centuries.