diff --git a/tla+-mode.el b/tla+-mode.el
index 76afda6..75c117c 100644
--- a/tla+-mode.el
+++ b/tla+-mode.el
@@ -344,10 +344,10 @@
 
 (defconst tla+-font-lock-keywords
   (list
-   '("\\<\\(MODULE\\|CONSTANTS?\\|UNCHANGED\\|VARIABLES?\\|THEOREM\\|LOCAL\\|ASSUME\\|EXTENDS?\\)\\>"
+   '("\\<\\(MODULE\\|CONSTANTS?\\|UNCHANGED\\|VARIABLES?\\|THEOREM\\|LOCAL\\|ASSUME\\|LET\\|EXTENDS?\\)\\>"
      . font-lock-builtin-face)
    '("\\<\\(TRUE\\|FALSE\\|OTHER\\|BOOLEAN\\|DOMAIN\\)\\>" . font-lock-type-face)   
-   '("\\<\\(CONSTANT\\|SUBSET\\|ENABLED\\|UNCHANGED\\|INSTANCE\\|WITH\\|EXCEPT\\|UNION\\|DOMAIN\\|EXCEPT\\|IF\\|THEN\\|ELSE\\|CHOOSE\\)\\>" . font-lock-keyword-face)
+   '("\\<\\(CONSTANT\\|SUBSET\\|ENABLED\\|UNCHANGED\\|INSTANCE\\|WITH\\|EXCEPT\\|UNION\\|IN\\|DOMAIN\\|EXCEPT\\|IF\\|THEN\\|ELSE\\|CHOOSE\\)\\>" . font-lock-keyword-face)
    '("\\\\\\*.*$" . font-lock-comment-face)
    '("(\\*.*\\*)" . font-lock-comment-face)
    '("\\('\\w*'\\)" . font-lock-variable-name-face)
@@ -424,6 +424,9 @@ Operation:
 This function starts the `xdvi' utility and opens the TLA+
 specification file as DVI.  It must be created beforehand
 with the `tla+-run-tlatex-dvi'.
+
+The argument BUFFERNAME is a TLA+ Buffer that will be opend
+as DVI file.
 "
   (interactive "b")
   (save-excursion