-<li><b>Exclude Groups</b> group box allows to ignore the nodes which
-belong to the specified mesh groups.
+<li>Activation of <b>No merge of corner and medium nodes of quadratic
+ cells</b> check-box prevents merging medium nodes of quadratic
+ elements with corner nodes. This check-box is enabled provided
+ that the selected mesh includes quadratic elements.</li>
+<li><b>Exclude groups from detection</b> group allows to ignore the
+ nodes which belong to the specified mesh groups. This control is
+ active provided that the mesh includes groups.</li>
+<li><b>Nodes to keep during the merge</b> group allows to specify
+ nodes to keep in the mesh. (By default a node being the first in a
+ group of coincident nodes is kept.) It is possible to either select
+ nodes in the Viewer or select groups of any element type whose nodes
+ will be kept.
+ <ul>
+ <li>\a Selection button activates selection of nodes to keep.</li>
+ <li><b>Nodes</b> button activates selection of nodes in the
+ Viewer.</li>
+ <li><b>Groups and sub-meshes</b> button activates selection of
+ groups and sub-meshes.</li>
+ <li>\b Add button adds selected nodes or groups to the list.</li>
+ <li> Nodes or groups selected in the list can be removed using \b
+ Remove button.</li>
+ </ul>
+</li>