A source " that was created later by someone who did not experience first-hand or participate in the events or conditions you’re researching. For the purposes of a historical research project, secondary sources are generally scholarly books and articles. Also included would be reference sources like encyclopedias" 

— University of Illinois Library, 2006.

Suggested keywords and subjects in the catalog:

• reconstruction--u s history 1865 1877
• slaves--emancipation--united states
• united states, bureau of refugees, freedmen, and abandoned lands
• african americans--history--1863-1877

Some searches to try:

• freedmen's bureau and education in JSTOR
• emancipation and southern states in America: History and Life