Added link to backend-writing.txt.

contrib.html

@@ -78,16 +78,20 @@
     </p>
 
     <p>
-      If you intend to write a backend: contact the <a href="mailing-lists.html">sane-devel mailing
-      list</a> and let us know. Get all the information about your scanner that's available: chipset
-      application manual (sometimes it's on the web), Windows drivers used (sometimes they tell
-      which chipset is used), programmer's information (if the manufacturer provides those). If you
-      don't have enough information about the protocol used by the scanner, <a
-      href="http://www.meier-Geinitz.de/sane/misc/develop.html">try to find out what the MS Windows
-      driver does</a>.  For basic information about how SANE works, get the latest <a
-      href="cvs.html">development version of SANE</a>, read man sane and
-      doc/backend-writing.txt. Also have a look at existing backends, e.g. one of the USB backends,
-      if you want to support a USB scanner.
+      If you intend to write a backend: contact the <a
+      href="mailing-lists.html">sane-devel mailing list</a> and let us know. Get
+      all the information about your scanner that's available: chipset
+      application manual (sometimes it's on the web), Windows drivers used
+      (sometimes they tell which chipset is used), programmer's information (if
+      the manufacturer provides those). If you don't have enough information
+      about the protocol used by the scanner, <a
+      href="http://www.meier-geinitz.de/sane/misc/develop.html">try to find out
+      what the MS Windows driver does</a>.  For basic information about how SANE
+      works, get the latest <a href="cvs.html">development version of SANE</a>,
+      read man sane and <a
+      href="backend-writing.txt">doc/backend-writing.txt</a>. Also have a look
+      at existing backends, e.g. one of the USB backends, if you want to support
+      a USB scanner.
     </p>
 
     <h2>Writing a Frontend</h2>