This document discusses various sources of information that can be used for research. It identifies primary sources such as interviews, experiments, observations, and questionnaires that provide first-hand information. Secondary sources include printed materials like books, journals, newspapers, magazines, and documents. The importance of these sources is that they allow researchers to establish facts, reaffirm previous work, solve problems, develop theories, and support hypotheses. The document encourages using a variety of sources, both primary and secondary, when conducting library or other research.