Q. For author-date parenthetical text references, CMOS 13.123 says to list “as many [authors] as needed to distinguish the references.” My reference list includes two articles where the first seven authors are the same. In that case, can I use the letters instead of listing more authors? The articles are both from 2006 in the journal Latin American Antiquity: “Smokescreens in the Provenance Investigation of Early Formative Mesoamerican Ceramics” and “Methodological Issues in the Provenance Investigation of Early Formative Mesoamerican Ceramics.”
A. Yes, you can use letters to differentiate the two articles in your text. Per CMOS 13.107, a source by more than six authors would be listed in your references by the first three, followed by et al. Because the first three authors are identical for those two articles (each of which lists thirteen authors), adding a and b after the year of publication would distinguish them in the text. Here are the reference list entries (in alphabetical order by title; see 13.114) and text citations:
Neff, Hector, Jeffrey Blomster, Michael D. Glascock, et al. 2006a. “Methodological Issues in the Provenance Investigation of Early Formative Mesoamerican Ceramics.” Latin American Antiquity 17 (1): 54–76. https://doi.org/10.2307/25063036.
Neff, Hector, Jeffrey Blomster, Michael D. Glascock, et al. 2006b. “Smokescreens in the Provenance Investigation of Early Formative Mesoamerican Ceramics.” Latin American Antiquity 17 (1): 104–18. https://doi.org/10.2307/25063039.
(Neff et al. 2006a)
(Neff et al. 2006b)
Alternatively, you could cite by title in the text (and omit the letters in the reference list entries and text citations):
(Neff et al., “Methodological Issues,” 2006)
(Neff et al., “Smokescreens,” 2006)
But the letters are more concise.