The information you provide that directs the reader to the source is called a citation . When you supply this information, you are citing your source. Any source from which you use information must be cited. Generally speaking, you are required to cite sources for all facts and ideas that you find in your research and that you did not know, think, or believe before beginning your research. Cite all facts that are not common knowledge.
Common knowledge consists of that information which is generally known.
A fact can be considered common knowledge if it is not unusual, is found in a number of standard sources, and does not vary from source to source. Therefore, even if you did not know before you began your research that Shakespeare wrote King Lear , you would not need to document this fact. If you are in doubt as to whether or not a fact should be cited, it is advisable to go ahead and cite it. If you are unsure if a particular saying is common enough to make citation unnecessary, find it s source by looking it up in a book of quotations such as Bartlett s Familiar Quotations so that you can cite it. Cite all ideas that you find in your research including those that you may have already had before you began your research .