Make sure that the first appearance of an author's work has all of the required information. This usually includes the author's name, page numbers, publication dates and title.
Consult writing guides on how to cite subsequent references to the same text. Most style guides, such as the American Psychological Association (APA) guide, demand that a person reference an author either within a sentence or at the end of the sentence within parenthesis, after the full reference has been given once. Sometimes the year of publication may follow the name of the author within a parenthetical citation.
Use footnotes or endnotes to refer back to previously cited material. Some formats do not allow people to use footnotes or endnotes and so you should check with your supervisor or professor to be certain that this is an acceptable method. In footnotes or endnotes, you can shorten the lengthy first citation in all subsequent references by typing either the website address or author's name and page number.
Use "ibid" as an abbreviation for "ibidem," which is a term that indicates that a reference has previously been cited in a paper or research document. People typically write "ibid" in place of footnotes. It acts as a shorthand for referring to sources.
Consult a professor or supervisor regarding the proper methodology for citing previously cited sources. They will gladly tell you the proper procedure for citing these sources.