Square brackets, often simply called brackets, are more disconnective than parentheses. They may be used in these cases:

1. to enclose material inserted into the text by an editor or a critical reviewer, not the author:
   
   
   The Harvey Formation [referred to as the Landing Formation, below] can be recognized at three localities in the area.
   
   
   
2. to enclose such phrases as [to be continued], [continued on page 10], [sic].
   
   
   
3. to enclose translations of titles.
   
   
   
4. to enclose a second set of parenthetical material inside material already enclosed by parentheses:
   
   
   (More controversial views were published recently [see Smith, 1990; Jones, 1991].)

If the second material is slight, such as an initial or number, it may be enclosed in a second set of parentheses instead or brackets of other shapes such as those used in the mathematics and optics field (braces):