Use brackets to set off an explanatory reference, your owncomments, or corrections within material you are quoting.
According to Smith, "Proton energy levels [in theaccelerator] are consistently higher than expected."
[These comments were made before Brodier became aware ofLightman's experiments.]
Unless the documentation style you are followingspecifies otherwise, use the Latin term sic in bracketsto indicate that material in a quotation is incorrect.
Freedman stated, "Various Indo-European languages such asRumanian, Hindi, Hungarian [sic], and Serbian exhibitsimilar morphological patterns."[Hungarian is not anIndo-European language.]
Use brackets to enclose parenthetical material that is withinmaterial already in parentheses.
The first extant cosmological theories were developed bythe early Babylonians and Greeks. (See Alan Lightman, AncientLight [Cambridge: Harvard University Press], pp.5-9.)
Use brackets to indicate the isotope of a specific chemical.
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