Improve readability of Optional VLR section intro.

Author: esilvia

source/04_optional_vlrs.txt

@@ -7,11 +7,9 @@
 Optional VLR Definitions
 --------------------------------------------------------------------------------
 
-LAS 1.5 defines Variable Length Records (VLRs) in :ref:`vlrdef_label` and EVLRs
-in :ref:`evlrdef_label`. Definitions for official VLRs as part of the specification 
+Definitions for official :ref:`vlrdef_label` and :ref:`evlrdef_label` 
 are provided in this section as a means to extend the LAS file format.
-
-Additional VLR definitions contributed by the LAS Working Group and the 
+Additional (E)VLR definitions contributed by the LAS Working Group and the 
 LAS community can be found on the official LAS wiki: https://github.com/ASPRSorg/LAS/
 
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