-united. You can click on an triangle in the 3D viewer and it will be
-highlighted. After that click the \b Add button and the ID of this
-triangle will be added to the list. To remove a selected element or
-elements from the list click the \b Remove button. The \b Sort button allows
-to sort the list of IDs. The <b>Set filter</b> button allows to apply a
-definite filter to selection of triangles.</li>
-<li><b>Apply to all</b> radio button allows to modify connectivity and
-type of all triangles of the currently displayed mesh or submesh.</li>
-<li>\b Criterion menu allows to apply the operation only to those
-object which meet the chosen criterion (from the list of Quality
-Controls, i.e. Skew, Warping, Minimum Angle, etc.)</li>
-<li><b>Select from</b> set of fields allows to choose a submesh or an
-existing group whose triangle elements will be automatically added to
-the list.</li>
+ united. You can click on a triangle in the 3D viewer and it will be
+ highlighted. After that click the \b Add button and the ID of this
+ triangle will be added to the list. To remove a selected element or
+ elements from the list click the \b Remove button. The \b Sort button allows
+ to sort the list of IDs. The <b>Filter</b> button allows to apply a
+ definite \ref filtering_elements "filter" to selection of triangles.</li>
+<li><b>Apply to all</b> radio button allows to apply the operation to
+ all triangles of the selected mesh.</li>
+<li><b>Preview</b> provides a preview in the viewer.</li>
+<li>\b Criterion menu allows to choose a quality criterion,
+ which will be optimized to select triangles to unite.</li>
+<li><b>Select from</b> set of fields allows to choose a sub-mesh or an
+ existing group whose triangle elements then can be added to the
+ list.</li>