This document discusses secondary data sources for research. Secondary data is data that was collected by someone else for another purpose. It has advantages like being inexpensive and rapid to obtain, but disadvantages like uncertain accuracy and potentially being outdated. When using secondary data, researchers should evaluate if the data is applicable to their research questions, population, and time period of interest. Common objectives for using secondary data include fact finding, model building, and data-based marketing. The document provides examples of internal, external, government, and commercial secondary data sources.