How you cite always depends on the required citation style. Examples below are given for MLA and APA styles from the Purdue OWL:
MLA Style
An Editorial & Letter to the Editor
Cite as you would any article in a periodical, but include the designators "Editorial" or "Letter" to identify the type of work it is.
"Of Mines and Men." Editorial. Wall Street Journal, eastern edition, 24 Oct. 2003, p. A14.
Hamer, John. Letter. American Journalism Review, Dec. 2006/Jan. 2007, p. 7.
APA Style
Letter to the Editor
Moller, G. (2002, August). Ripples versus rumbles [Letter to the editor]. Scientific American, 287(2), 12.
