Governments and non-governmental agencies generate reports and statistics on many topics. They also undertake investigations and conduct hearings.
As classified documents are released to the public, they may appear in any of several databases or web sites. No single site or database provides complete coverage, so the diligent researcher will consult them all.
"The Foreign Relations of the United States series presents the official documentary historical record of major US foreign policy decisions and significant diplomatic activity. The series, which is produced by the State Department's Office of the Historian, began in 1861 and now comprises more than 350 individual volumes. The volumes published over the last two decades increasingly contain declassified records from all the foreign affairs agencies." [from the State Dept. website]
There are several online versions of parts or all of this series:
FOIA amendments signed into law in 1994 added a requirement that agencies must establish an Electronic FOIA (EFOIA) Reading Room. The links below take you to FOIA Reading Rooms for several related government agencies.
To search for first-hand accounts of events, try searching for your topic/keywords (including country/region) AND terms such as: interviews, case studies, oral histories, narratives, memoirs, correspondence, letters, diaries, etc. Use this strategy to search GOOGLE (to bring up NGO reports, YouTube videos, digital archives, etc.) as well as the library search box (which will bring up published books and articles that include this type of information).
The University of New Mexico's Center for Southwest Research (CSWR) and Special Collections specializes in preserving historical manuscripts, books, photographs, architectural drawings, recordings, and other library materials relating to New Mexico, the Southwestern U.S., and Latin America. It also houses the UNM University Archives, as well as a collection of rare books on various topics from around the world.