Update textbook.en.md

00.brainstorming-pedagogical-teams/45.synthesis-structuring/electromagnetism/n1/textbook.en.md

@@ -25,4 +25,25 @@ What knowledge on this topic is useful in everyday life or for understanding fut
 What worries them or scares them?
 What amazes and amazes them?
 
-Chapter titles should be words from everyday life. 
+Chapter titles should be words from everyday life. 
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+
+#### To participate
+
+The different proposals are numbered: they start with:
+[BRST-EMG1-number]: Title <br>
+_BRST-EMG1 for Brainstorming STructure ElectroMaGnétismme level 1)_
+
+To **add a proposition, create it** between 2 propositions, or in the following (following 
+the logic of the proposition). To do this, start with: <br>
+*a new [BRST-EMG1-number] + (three initials in brackets representing you) + Title*
+
+To **react to an existing proposal**, add your comment after the others
+starting with three initials in brackets representing you:
+(CLM): comment of such
+*(my initials): my comment*
+
+_or send an email specifying:_
+_the reference [BRST-EMG1-number], which identifies me (my initials) and my comment_
+_(+ a title if it's a new proposition)_ 
+
+----------------------------------------
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