Citation, Documentation of Sources
Q. How do I cite in text two works in the same year by authors with the same surname? I have (MacDonald 1999) for both K. A. MacDonald and R. H. MacDonald, each of whom wrote an article that year. It seems awkward to refer to them as (e.g.) “R. MacDonald” when I’ve given none of the other authors a first initial.
A. It may strike you as awkward, but it is conventional in such cases to clarify by adding initials or full names if necessary. Please see CMOS 15.22: “Where two or more works by different authors with the same last name are listed in a reference list, the text citation must include an initial (or two initials or a given name if necessary).”