A credible source is extremely necessary to establish your own credibility and ethos with the reader. Sources you deem credible might not be sources others deem credible. You must be careful about where and whom you choose for your source, keeping a keen eye on bias, use of informal language, and lack of evidence or proper citation of sources.
In general, it is best to use an academic source such as a scientific paper or research study conducted by an accredited institution. These are often published in journals and are subject to "peer review". The next level of credible source is a trusted publication such as the New York Times, London Times, Christian Science Monitor, etc. Find well established publications with a reputation for accuracy and high editorial standards. The web is not considered a good source unless the URL ends in .gov or .edu. Even websites ending in .org can have dubious content. Wikipedia is not considered a legitimate source because anyone can submit and change the information. Avoid hear-say, blogs, and comment sites. Blurtit is a bad source.
In general, it is best to use an academic source such as a scientific paper or research study conducted by an accredited institution. These are often published in journals and are subject to "peer review". The next level of credible source is a trusted publication such as the New York Times, London Times, Christian Science Monitor, etc. Find well established publications with a reputation for accuracy and high editorial standards. The web is not considered a good source unless the URL ends in .gov or .edu. Even websites ending in .org can have dubious content. Wikipedia is not considered a legitimate source because anyone can submit and change the information. Avoid hear-say, blogs, and comment sites. Blurtit is a bad source.