Historians conduct research and analysis for governments, businesses, nonprofits, historical associations, and other organizations. They use a variety of sources in their work, including government and institutional records, newspapers, photographs, interviews, films, and unpublished manuscripts such as personal diaries and letters. They also may process, catalog, and archive these documents and artifacts. Most historians present and interpret history for the public. They often trace and build a historical profile of a particular person, area, idea, organization, or event. Once their research is complete, they present their findings through articles, books, reports, exhibits, websites, and educational programs. Historians need a master’s degree or Ph.D. for most positions. Many historians have a master’s degree in history or public history, which takes 2 years beyond a four-year bachelor's degree to complete. Others complete degrees in related fields, such as museum studies, historical preservation, or archival management. Many programs require an internship or other onsite work experience as a part of the degree program.