diff --git a/collects/algol60/cfg-parser.rkt b/collects/algol60/cfg-parser.rkt
index 04a2297..b3e2573 100644
--- a/collects/algol60/cfg-parser.rkt
+++ b/collects/algol60/cfg-parser.rkt
@@ -627,7 +627,7 @@
 								  l))))
 						  pats (caddr old-list))))
 				     nt-ids patss)
-				    ;; Build a definiton for each non-term:
+				    ;; Build a definition for each non-term:
 				    (loop (cdr clauses)
 					  cfg-start
 					  (map (lambda (nt pats handles $ctxs)
diff --git a/collects/parser-tools/lex.rkt b/collects/parser-tools/lex.rkt
index e9983ab..2db2ecb 100644
--- a/collects/parser-tools/lex.rkt
+++ b/collects/parser-tools/lex.rkt
@@ -252,7 +252,7 @@
                                       ;; including a match at the current state
                                       (longest-match-action 
                                        (vector-ref actions start-state))
-                                      ;; how many bytes preceed char
+                                      ;; how many bytes precede char
                                       (length-bytes 0)
                                       ;; how many characters have been read
                                       ;; including the one just read
diff --git a/collects/parser-tools/parser-tools.scrbl b/collects/parser-tools/parser-tools.scrbl
index 90debe4..5f2a43a 100644
--- a/collects/parser-tools/parser-tools.scrbl
+++ b/collects/parser-tools/parser-tools.scrbl
@@ -22,6 +22,10 @@ style lexer and parser generators.
 
 @section{Lexers}
 
+@section-index["lex"]
+@section-index["scanning"]
+@section-index["scanner"]
+
 @defmodule[parser-tools/lex]
 
 @; ----------------------------------------
@@ -484,6 +488,8 @@ the right choice when using @scheme[lexer] in other situations.
 
 @section{Parsers}
 
+@section-index["yacc"]
+
 @defmodule[parser-tools/yacc]
 
 @defform/subs[#:literals (grammar tokens start end precs src-pos
diff --git a/collects/parser-tools/private-yacc/grammar.rkt b/collects/parser-tools/private-yacc/grammar.rkt
index dd71a88..fe20c5a 100644
--- a/collects/parser-tools/private-yacc/grammar.rkt
+++ b/collects/parser-tools/private-yacc/grammar.rkt
@@ -12,7 +12,7 @@
   (define-struct prod (lhs rhs index prec action) (make-inspector))
 
   ;; The dot-pos field is the index of the element in the rhs
-  ;; of prod that the dot immediately preceeds.
+  ;; of prod that the dot immediately precedes.
   ;; Thus 0 <= dot-pos <= (vector-length rhs).
   (define-struct item (prod dot-pos) (make-inspector))