[...]

Single square brackets: text written by the scribe, but disappeared since, and completed by us.

«...»

Double angular brackets: uncertain reading. (Unicode 00AB and 00BB)

(...)

Round brackets (parentheses): the solution of real abbreviations.

<...>

Angular brackets: text left out by the scribe, and completed by us.

[[...]]

Double square brackets: erasures, deleted by the scribe and to be completed by us. (Unicode 301A and 301B)

{...}

Curly brackets: text written by mistake. In case a misspelt word (in curly brackets) was corrected by the scribe himself, the correct word follows the misspelt one without brackets. If the editor corrected the word, the corrected word follows in angular brackets.
Abbreviations: The solution will follow in round brackets.