A manual for writers of research papers, theses, and dissertations, 7th edition - Kate L. Turabian 2007

Brackets
Spelling
Part III. Style 20 spelling

Brackets are most often used in quotations, to indicate changes made to a quoted passage (see 25.3 for examples). They can also be used to enclose a second layer of parenthetical material within parentheses.

He agrees with the idea that childhood has a history (first advanced by Philippe Ariès [1914—84] in his book Centuries of Childhood [1962]).