_____________              _____________              _____________
|             |            |             |            |             |
|     879     |    <---    |     865     |    --->    |     952     |
|_____________|            |_____________|            |_____________|

.". .nsm. -->              .pt. -->  .ht.

msn <-->  th <-            ->  pt <-->  "

ht -->  tldf
" pt <-->  th <            -->  smn
.ht. -->  .tp.             -->  .smn. -->              .".
th <-->  tdfl