A primary source is an original document or other material that has not been changed in any way.[1] It is a reliable first-hand account usually written at or near the time the event(s) occurred.[2] Usually it was produced by someone with direct personal knowledge of the events that are described. It is used as an original source of information about the topic.[3] Primary sources are distinguished from secondary sources. Secondary sources are documents based on primary sources.[4] Thus, a memoir of a participant in an event is a primary source, whilst a history of that event based on several memoirs is a secondary source. Different kinds of work have slightly different definitions of a primary source.[5] In journalism, for example, a primary source can also be a person.