A study of cultural history could include fictional sources such as novels or plays. In a broader sense, primary sources also include artifacts such as photographs, news reels, coins, paintings, or buildings created at the time. Historians may also review archaeological artifacts and oral reports and interviews. Written sources can be divided into three types.  In the United States, digital copies of primary sources can be extracted from a number of locations. The Library of Congress holds several digital collections where they are accessible. Some examples are American Memory and Chronicling America. The National Archives and Records Administration also has digital collections in digital vaults. The Digital Public Library of America searches the digitized primary source collections of many libraries, archives, and museums. The Internet Archive also contains primary sources in many formats. In many fields and contexts, such as historical writing, it is almost always advisable to use primary sources whenever possible, and “if none are available, only with great caution can [the author] continue to use secondary sources.”  In addition, primary sources avoid the problem inherent in secondary sources, where any new author can distort and reshoot the results of the authors cited above.  In the scientific literature, the purpose of source classification is to determine the independence and reliability of sources.  Although the terms primary source and secondary source come from historiography to understand the history of historical ideas, they have been applied to many other fields.
For example, these ideas can be used to trace the history of scientific theories, literary elements, and other information passed from one author to another. However, primary sources – especially those from before the 20th century – can bring hidden challenges. “Primary sources, in fact, are usually fragmentary, ambiguous, and very difficult to analyze and interpret.”  The outdated meanings of colloquial words and social context are among the pitfalls that await the newcomer to history. For this reason, the interpretation of primary texts is usually taught as part of an advanced college or postgraduate college history course, although advanced self-study or informal training is also possible. Primary sources are often incomplete and have little context. Students must use previous knowledge and work with multiple resources to find patterns and build knowledge. History as an academic discipline is based on primary sources evaluated by the research community who report their findings in books, articles, and articles. Arthur Marwick says, “Primary sources are absolutely fundamental to history.”  Ideally, a historian would use all available primary sources created by those involved at the time of the study. In practice, some sources have been destroyed, while others are not available for research. Perhaps the only eyewitness accounts of an event are memoirs, autobiographies, or oral interviews recorded years later. Sometimes the only evidence relating to an event or person in the distant past was written or copied decades or centuries later.
Manuscripts that are sources of classical texts can be copies of documents or fragments of copies of documents. This is a common problem in classical studies, where sometimes only a summary of a book or letter has survived. Possible difficulties with primary sources mean that history is usually taught in schools using secondary sources. Primary sources help students relate to past events in a personal way and promote a deeper understanding of history as a set of human events. Because primary sources are incomplete snippets of history, each represents a mystery that students can only explore by finding new evidence. A story whose author draws conclusions from sources other than primary sources, or secondary sources that are in fact based on primary sources, is by definition fiction and not a story at all. In some cases, the reason why a text has been identified as a “primary source” may result from the fact that there is no copy of the original source material or that it is the oldest surviving source for the information cited.  In historiography, when the study of history is subjected to historical examination, a secondary source becomes a primary source. For a biography of a historian, that historian`s publications would be primary sources. Documentaries can be considered a secondary or primary source, depending on the extent to which the filmmaker modifies the original sources. Ask if this source is consistent with other primary sources or with what students already know. In the UK, the National Archives offers a consolidated search of its own catalogue and a variety of other archives listed in the Archives Access Index. Digital copies of various classes of documents at the National Archives (including wills) are available at DocumentsOnline. Most of the documents available relate to England and Wales. Some digital copies of primary sources are available from the National Archives of Scotland. Many collections from county registrars are included in Access to Archives, while others have their own online catalogs. Many county registrars will provide digital copies of the documents. Participants and eyewitnesses may misunderstand events or distort their reports intentionally or unintentionally in order to improve their own image or meaning. Such effects can increase over time as people create a narrative that may not be accurate.  For each source, whether primary or secondary, it is important for the researcher to assess the extent and direction of the bias.  For example, a government report may be an accurate and unbiased description of events, but it may be censored or altered for propaganda or cover-up purposes.
Facts can be distorted to portray opposite parties in a negative light. Lawyers are taught that the evidence in a court case may be true, but can always be distorted to support or reject the position of either party. When analyzing primary sources, students move from observations and concrete facts to questions and conclusions about materials. Errors can be corrected in secondary sources, which are often peer-reviewed, can be well documented, and are often written by historians working in institutions where methodological accuracy is important for the future of the author`s career and reputation. Historians consider the accuracy and objectivity of the primary sources they use, and historians subject primary and secondary sources to a high degree of examination. A primary source such as a journal entry (or the online version, a blog) at best reflects only a person`s opinion about events, which may or may not be true, accurate, or complete. Primary sources are distinct from secondary sources that cite, comment on, or rely on primary sources. In general, reports written retrospectively with the advantage of retrospect are secondary.  A secondary source can also be a primary source, depending on how it is used.  For example, memoirs would be considered a primary source in research on their author or their friends characterized therein, but the same memoirs would be a secondary source if they were used to examine the culture in which their author lived. “Primary” and “secondary” should be understood as relative terms, with sources classified according to specific historical contexts and what is being investigated. : 118–246  However, a primary source is not necessarily an authority or better than a secondary source.
There may be tacit biases and unconscious views that distort historical information. In scientific writing, an important objective of the classification of sources is to determine their independence and reliability.  In contexts such as historical writing, it is almost always advisable to use primary sources, and that “if none are available, it is only possible with great caution [the author] to use secondary sources.”  Sreedharan believes that primary sources have the most direct connection to the past and that they “speak for themselves” in a way that cannot be captured by filtering out secondary sources.  Putting young people in close contact with these unique, often deeply personal documents and objects can give them an idea of what it was like to be alive in a bygone era. Helping students analyze primary sources can also spark curiosity and improve critical thinking and analytical skills. For centuries, popes have used Constantine`s false gift to strengthen the secular power of the papacy. The first forgeries include fake Anglo-Saxon documents, a series of 11th and 12th century forgeries made by monasteries and abbeys to support a land claim where the original document had been lost or had never existed.