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 482b33594..f82b01e7f 100644
--- a/10.brainstorming-innovative-courses/intercambio-curso-electromagnetismo/textbook.en.md
+++ b/10.brainstorming-innovative-courses/intercambio-curso-electromagnetismo/textbook.en.md
@@ -186,16 +186,19 @@ ES : sistema de coordenadas cartesianas   <br>
 FR : système de coordonnées cartésiennes   <br>
 EN : Cartesian coordinate system
 
-$`\nabla =  \overrightarrow{e_x}\,\dfrac{\partial}{\partial x}+ \overrightarrow{e_y}\,\dfrac{\partial}{\partial y}
-+\overrightarrow{e_z}\,\dfrac{\partial}{\partial z} `$  
+$`\nabla =  \vec{e_x}\,\dfrac{\partial}{\partial x}+ \vec{e_y}\,\dfrac{\partial}{\partial y}
++\vec{e_z}\,\dfrac{\partial}{\partial z} `$  
 , or 
 $`\nabla = \overrightarrow{e_x}\,\dfrac{\partial}{\partial x}+\overrightarrow{e_y}\,\dfrac{\partial}{\partial y}
-+\overrightarrow{e_z}\,\dfrac{\partial}{\partial z} `$ <br>
++\overrightarrow{e_z}\,\dfrac{\partial}{\partial z}`$ 
+, or more
+$`\overrightarrow{\nabla} = \overrightarrow{e_x}\,\dfrac{\partial}{\partial x}+\overrightarrow{e_y}\,\dfrac{\partial}{\partial y}
++\overrightarrow{e_z}\,\dfrac{\partial}{\partial z} `$ 
 ES : operador nabla   <br>
 FR : opérateur nabla   <br>
 EN : nabla operator
 
-$`\overrightarrow{grad}\;f=\nabla\;f`$, $`\overrightarrow{\nabla}\;f`$ better, no?   <br>
+$`\overrightarrow{grad}f=\nablaf`$, $`\overrightarrow{\nabla}f`$ better, no?   <br>
 ES : gradiente   <br>
 FR : gradient   <br>
 EN : gradient
@@ -206,6 +209,13 @@ FR : divergence   <br>
 EN : divergence   <br>
 $`div\;\overrightarrow{U}=\lim_{V\leftrightarrow0}\;\dfrac{1}{V}\;\displaystyle\oiint_{S\leftrightarrow V}\overrightarrow{U}\cdot\overrightarrow{dS}`$ 
 
+$`rot\times\overrightarrow{U}`$, but $`\overrightarrow{rot}\times\overrightarrow{U}`$ better, no?   <br>
+in some English texts : $`curl\times\overrightarrow{U}`$   <br>
+$`\overrightarrow{\nabla}\times\overrightarrow{U}`$ or $`\overrightarrow{\nabla}\land\overrightarrow{U}`$    <br>
+ES : rotacional de un vector  <br>
+FR : rotationnel d'un vecteur   <br>
+EN : rotation of a vector (= curl of a vector )
+
 ES : escalar = número real o complexo + unidad de medida?   <br>
 FR : scalaire = nombre réel ou complexe + unité de mesure   <br>
 EN : scalar = real or complex number + measurement unit