The definition of a credible source varies by subject, but in general, for academic writing, a credible source is one that is neutral and supported by evidence. Always use and reference reputable sources while writing a research paper. These can be books, magazines, newspapers, or websites. In journalism, a source is said to be credible if they are independent from the topic being reported on. This means that they cannot be influenced by any third party including the reporter's employer or anyone else. If a source appears to have an interest in how they are being reported upon, then this might indicate that they are not independent enough and should be treated with more caution. For example, if a newspaper reports that "source close to the situation" says X, it is likely that someone at the newspaper believes what they are saying is true. However, if another newspaper reports similar information from a different source, this would be considered two different sources with two different views on X. In conclusion, sources are credible when they are independent from the topic under consideration. This independence can be shown through physical distance (i.e., a news source is independent if it is not contained within the same building as your academic institution) as well as professional relationships (i.e., a news source is independent if they do not work for your academic institution).