Update textbook.en.md

00.brainstorming-pedagogical-teams/45.synthesis-structuring/classical-mechanics/n4/10.brainstorming/textbook.en.md

@@ -8,6 +8,12 @@ lessons:
       order: 3
 ---
 
+This level 4 brainstorming can be seen in its multilingual version at: 
+
+https://m3p2.com/polyglot/brainstorming-pedagogical-teams/synthesis-structuring/classical-mechanics/n4/brainstorming
+
+--------------------------------
+
 #### Brainstorming to structure a theme "Classical mechanics" : level 4
 
 --------------------------------