logical dimension 
              <em>&lt;tdim&gt;</em>. In those groups, the reference <em>&lt;old1&gt;</em> will be changed by <em>&lt;new1&gt;</em>,
              etc., and finally <em>&lt;oldn&gt;</em> by <em>&lt;newn&gt;</em>. 
              Be aware that new references can be changed again when appear later in the list as an old reference. The values must be separated by commas 
              without blank spaces and enclose them in square brackets. Please, be aware that, if you want to change referenc