<\body> It is possible to gradually undo the changes you made in a document from the moment that you launched . This can be done via or using the keystrokes or . Undone changes can be ``redone'' using or . In order to save memory, the number of successive actions which can be undone is limited to 100 (by default). It is possible to increase this number by adding a command like\ <\verbatim> \ \ \ \ (set-maximal-undo-depth 1000) in our personal initialization file (see ). When specifying a negative number as your maximal undo depth, any number of actions can be undone. <\initial> <\collection>