Sometimes people need "primary sources" for their research. Primary sources are information materials either from the time in question, or accounts of that time made later on by participants in it.
For example, if you were researching WWI, magazine articles from 1914-1918 would be primary sources. You could locate them using our Readers Guide to Periodical Literature, which goes back to 1899 (REF AI3 .R48.)
Or, for books, try searching our catalog, doing for example a subject keyword search of world war 1914 personal narratives to find personal accounts of soldiers and other participants experiences in the war.
There are many more possibilities, ask one of us to learn more about them!