Explaining why it seems that we do are not updating the images

Author: ocampana-videotec

doc/equations/PTZ/lat_1.xml

@@ -3,4 +3,4 @@
     <mml:mi mathvariant="normal">Lat</mml:mi>
     <mml:mn>1</mml:mn>
   </mml:msub>
- </mml:math>
+</mml:math>

doc/equations/README.md

@@ -5,3 +5,10 @@ This folder holds all the equations used in the specification documents. This is
 Each file contains one equation and must follow the MathML syntax. It is important to underline that files must have `.xml` extensions, otherwise XML calabash will not be able to parse the file.
 
 Upon pushing, the system will automatically generate in background the `.svg` files. You will receive the generated images with a successive pull.
+
+**Beware** that it may happen that upon editing the equations, the svg files are not updated. This happens whenever the new markup does not produce a change in the image. So far, it is know that
+
+* `⁡` or `⁡`
+* `mathvariant="normal"`
+
+will not trigger any change in the image.