diff --git a/src/SMDS/SMDS_VolumeTool.cxx b/src/SMDS/SMDS_VolumeTool.cxx
index 2c7c401cb..a2a8d2b11 100644
--- a/src/SMDS/SMDS_VolumeTool.cxx
+++ b/src/SMDS/SMDS_VolumeTool.cxx
@@ -292,27 +292,27 @@ static int QuadPenta_RE [5][9] = { // REVERSED -> EXTERNAL
 static int QuadPenta_nbN [] = { 6, 6, 8, 8, 8 };
 
 /*
-//                 13
-//         N5+-----+-----+N6
-//          /|          /|
-//       12+ |       14+ |
-//        /  |        /  |
-//     N4+-----+-----+N7 |           QUADRATIC
-//       |   | 15    |   |           HEXAHEDRON
-//       |   |       |   |
-//       | 17+       |   +18
-//       |   |       |   |
-//       |   |       |   |
-//       |   |       |   |
-//     16+   |       +19 |
-//       |   |       |   |
-//       |   |     9 |   |
-//       | N1+-----+-|---+N2
-//       |  /        |  /
-//       | +8        | +10
-//       |/          |/
-//     N0+-----+-----+N3
-//             11
+//                 13                                                         
+//         N5+-----+-----+N6                          +-----+-----+
+//          /|          /|                           /|          /| 
+//       12+ |       14+ |                          + |   +25   + |    
+//        /  |        /  |                         /  |        /  |    
+//     N4+-----+-----+N7 |       QUADRATIC        +-----+-----+   |  Central nodes
+//       |   | 15    |   |       HEXAHEDRON       |   |       |   |  of tri-quadratic
+//       |   |       |   |                        |   |       |   |  HEXAHEDRON
+//       | 17+       |   +18                      |   +   22+ |   +  
+//       |   |       |   |                        |21 |       |   | 
+//       |   |       |   |                        | + | 26+   | + |    
+//       |   |       |   |                        |   |       |23 |    
+//     16+   |       +19 |                        +   | +24   +   |    
+//       |   |       |   |                        |   |       |   |    
+//       |   |     9 |   |                        |   |       |   |    
+//       | N1+-----+-|---+N2                      |   +-----+-|---+    
+//       |  /        |  /                         |  /        |  /  
+//       | +8        | +10                        | +   20+   | +      
+//       |/          |/                           |/          |/       
+//     N0+-----+-----+N3                          +-----+-----+    
+//             11                              
 */
 static int QuadHexa_F [6][9] = {  // FORWARD
   { 0, 8, 1, 9, 2, 10,3, 11,0 },   // all face normals are external,