Fix unreadable sentence in block 031.

This clearly has some words missing.

blk/031

@@ -7,9 +7,9 @@ modified. "I:" prefix means "IMMEDIATE", that is, that this
 stack transformation is made at compile time.
 
 Word references (wordref): When we say we have a "word
-reference", it's a pointer to a word's *code link*. For
-example, the address that "' DUP" is a wordref, that is, a
-reference to the code link of the word DUP.
+reference", it's a pointer to a word's *code link*. For example,
+the address that "' DUP" puts on the stack is a wordref, that
+is, a reference to the code link of the word DUP.
 
 PF: Parameter field. The area following the code link of a
 word. For example, "' H@ 1+" points to the PF of the word H@.