diff --git a/00.brainstorming-pedagogical-teams/45.synthesis-structuring/40.electromagnetism/50.structure-example/40.n4/textbook.en.md b/00.brainstorming-pedagogical-teams/45.synthesis-structuring/40.electromagnetism/50.structure-example/40.n4/textbook.en.md
index cf25c6e8c..e9434bf9f 100644
--- a/00.brainstorming-pedagogical-teams/45.synthesis-structuring/40.electromagnetism/50.structure-example/40.n4/textbook.en.md
+++ b/00.brainstorming-pedagogical-teams/45.synthesis-structuring/40.electromagnetism/50.structure-example/40.n4/textbook.en.md
@@ -7,7 +7,8 @@ lessons:
     - slug: structure-example-234-electromagnetism
       order: 3
 ---
-
+<!--caligraphie de l'intégrale double curviligne-->
+$`\def\oint{\displaystyle\mathop{{\int}\mkern-16mu \scriptsize \bigcirc}}`$
 
 #### Guidance to structure this level 4