Citation, Documentation of Sources
Q. What is the order of dates in an in-text citation when more than one author is cited? Is it ascending by date? For example: (Martin 1986; Halliday 2000; Butt et al. 2003)? Or doesn’t the order matter?
A. The order in which author-date citations are given may depend on the order they were quoted or referred to in the text, or it may reflect the relative importance of the items cited. If neither criterion applies, alphabetical or chronological order may be appropriate. Unless citation order is prescribed by a particular journal style, the decision is the author’s and must not be edited without the author’s permission. Please see CMOS 15.30.