-<li><b>Coincident nodes</b> is a list of groups of elements for
- merging. After the operation all elements of each group will
- be united into one element.
+<li><b>Coincident nodes</b> is a list of groups of nodes for
+ merging. After the operation all nodes of each group will
+ be united into one node. The first node of a group is kept and
+ the others are removed.