The U.S. Government is the largest publisher in the world. Its publications are primary resources.
"Primary sources (sometimes referred to as "original" sources) provide first-hand testimony or direct evidence concerning a topic under investigation. They are created by witnesses or recorders who experienced the events or conditions being documented. Often these sources are created at the time when the events or conditions are occurring, but they can also include autobiographies, memoirs, and oral histories recorded later. Primary sources are characterized by their content, regardless of the format they are published in.
A wide range of primary sources are found in government documents: the hearings and debates of legislative bodies; the official text of laws, regulations and treaties; records of government expenditures and finances; statistical compilations such as census data; investigative reports; scientific data; and many other sources that touch virtually all aspects of society and human endeavor. "