XML : What is the equivalent of 'greater-than-equal-to' or 'less-than-equal-to' in XML?

I found this Use of Greater Than Symbol in XML where the answer is to use the following for 'greater-than' and 'less-than' respectively:

  > and <  

However, what should we use for 'greater-than-equal-to' and 'less-than-equal-to' ?

I already tried the following but it didn't work for me.

  ≥ and ≤