Fix typo

reference.htm

@@ -529,7 +529,7 @@ object representing the program.</p>
     - take a peek at the code if you want the gruesome details. Source lines may
     only start with line numbers or (as an extension) separators. Special statement
     parsing is done while lexing: <code>REM</code> consumes anything to the next
-    line break, and <code>DATA</code> statements yeild an array of strings
+    line break, and <code>DATA</code> statements yield an array of strings
     from the comma-delimited, optionally-quoted values in the source.
 </p>