brackets: editorial insertions and nested material
Square brackets inside a quotation, and brackets inside parentheses.
Use square brackets [ ] to mark words you have added to a quotation: He said the “plan [was] dead.” Use them for sic. For a parenthesis inside a parenthesis, American print prefers brackets inside the outer parentheses: (see Jones [2019]). Do not use brackets as fancy parentheses in ordinary sentences.
Examples
Use“The court [then] adjourned.”
Use(see the memo of May 12 [attachment B])
Avoid“The court then adjourned.” (If then is your insertion.)