diff --git a/10.brainstorming-innovative-courses/intercambio-curso-electromagnetismo/textbook.en.md b/10.brainstorming-innovative-courses/intercambio-curso-electromagnetismo/textbook.en.md
index f8d897033..9a244abda 100644
--- a/10.brainstorming-innovative-courses/intercambio-curso-electromagnetismo/textbook.en.md
+++ b/10.brainstorming-innovative-courses/intercambio-curso-electromagnetismo/textbook.en.md
@@ -166,12 +166,12 @@ ES : circulación de un vector <br>
 FR : circulation d'un vecteur <br>
 EN : circulation of a vector
 
-$`dA=dx\;dy`$ <br>
+$`dA = dx \, dy`$ <br>
 ES : elemento escalar de superficie  <br>
 FR : élément scalaire de surface (= surface élémentaire, surface infinitésimale) <br>
 EN : scalar surface element
 
-$`\overrightarrow{dA} = \overrightarrowc{e_n}\;dA = \overrightarrow{n}\;dA `$ <br>
+$`\overrightarrow{dA} = \overrightarrow{e_n}\;dA = \overrightarrow{n}\;dA `$ <br>
 ES : elemento vectorial de superficie  <br>
 FR : élément vectoriel de surface  <br>
 EN : vector surface element
@@ -184,8 +184,8 @@ ES : sistema de coordenadas cartesianas   <br>
 FR : système de coordonnées cartésiennes   <br>
 EN : Cartesian coordinate system
 
-$`\nabla =  \vec{e_x}\,\dfrac{\partial}{\partial x}+ \vec{e_y}\,\dfrac{\partial}{\partial y}
-+\vec{e_z}\,\dfrac{\partial}{\partial z} `$  
+$`\nabla =\vec{e_x}\,\dfrac{\partial}{\partial x} + \vec{e_y}\,\dfrac{\partial}{\partial y}
++\vec{e_z}\,\dfrac{\partial}{\partial z}`$  
 , or 
 $`\nabla = \overrightarrow{e_x}\,\dfrac{\partial}{\partial x}+\overrightarrow{e_y}\,\dfrac{\partial}{\partial y}
 +\overrightarrow{e_z}\,\dfrac{\partial}{\partial z}`$