[ ] Square brackets

This is right:
245 1 4 $aThe big one /$c[John Smith ... et al.].

This is wrong:
245 1 4 $aThe big one /c[John Smith ... [et al.]].

It is a tautology to have a square bracket inside a square bracket.

However:-
830 # 0 $a Research report (Cooperative Research Centre for Coal in Sustainable Development (Australia)) ; ‡v 42.

ALSO

correct
260 # # $a Suva [Fiji]

wrong
260 # # $a Suva, [Fiji] ie no comma

ALSO

correct
260 # # $a [Hobart, Tas. : $b Victoria Rigney], $c c2008.
Example from MARC standards: 260 ##$a[S.l. :$bs.n.,$c15--?]

wrong
260 # # $a [Hobart, Tas.] : $b [Victoria Rigney], $c c2008.


500 Do not use [ ] unless it is inside a quote i.e. " quoted words [ not quoted ] more quoted words"--T.p. verso.