Assignment

Hi,

We would like to change "from" and "subject" fields of assignement submission's email notification, but i can't find any characters chains on the page "Editing words or phrases" for "assignement.php" at "Administration ► Language ► Language editing"...i've looked in some other files i thought could be the good one but didn't find anything.
Is this in fact a template to modify or did i looked in wrong places ? i've searched forums and didn't find a thread about this.

Thanks in advance, Julien