Citing sources accomplishes several things. The author avoids being accused of plagiarism, the reader is able to cross-check information and it provides a sense of credibility for the arguments or facts the author is using in his document. Almost every piece of information can be cited, including books, magazines, articles, e-books, speeches and internal documents that are only meant to be read by office or authorized personnel. Cite internal documents in the text or in the bibliography.
Use the last name of the author. If the paper or report is published by multiple people, use the first last name listed, followed by the term "et al."
Determine the date of the report. You can use the day, month and year, or month and year, or simply the year, depending on the frequency of the letter or report.
Place the last name followed by the date in parentheses to correctly cite the internal document. For example, if the sentence is: At the direction of the Vice President of Operations, John Smalley, there will be no parking in the upper lot. Smalley(2006).
List the last name and first letter of the author followed by the phrase "Letter to author." Again, if there are multiple authors use the phrase "et al" after the first name. Using the above example, say the letter is written by John Smalley. It is cited as Smalley, J. Letter to author. Note the comma after the last name and period after the first initial of the first name. If this is an internal report, go to the next step.
List the full name of the report. Note, you are not listing individual authors for the bibliography citing of a report. For example, say the Acme Company released a cost basis report on a daily basis to employees. It is written as "Acme Cost Basis."
List the date in numeric form. Numeric form includes the corresponding month, day and year written out in four numbers separated by forward slashes. For example: 1/31/2011. This applies for both internal letters and reports. Additionally, list as much of this information as you have available. An internal newsletter only published monthly would only have a month and year.
List where the item is currently located in parentheses. List "Private collection" or a letter. For a report, list the archive collection or the place the report is located. For example, say Acme kept reports in the "Basement archives." Putting together examples from Steps 1 to 4 the internal documents is cited in the following manner:
Letter: Smalley, J. Letter to author 1/31/2011(Private collection).
Report: Acme Cost Basis 1/31/2011(Basement archives).