added reference to working with relative xpaths in the tutorial

docs/intro/tutorial.rst

@@ -321,6 +321,13 @@ that property here, so::
        desc = site.x('text()').extract()
        print title, link, desc
 
+.. note::
+
+   For a detailed description of using nested selectors see
+   :ref:`topics-selectors-nesting-selectors` and
+   :ref:`topics-selectors-relative-xpaths` in :ref:`topics-selectors`
+   documentation
+
 Let's add this code to our spider::
 
    from scrapy.spider import BaseSpider

docs/topics/selectors.rst

@@ -148,6 +148,7 @@ Here's an example used to extract images names from the :ref:`HTML code
      u'My image 4',
      u'My image 5']
 
+.. _topics-selectors-nesting-selectors:
 
 Nesting selectors
 -----------------
@@ -173,6 +174,8 @@ The ``x()`` selector method returns a list of selectors, so you can call the
     Link number 3 points to url [u'image4.html'] and image [u'image4_thumb.jpg']
     Link number 4 points to url [u'image5.html'] and image [u'image5_thumb.jpg']
 
+.. _topics-selectors-relative-xpaths:
+
 Working with relative XPaths
 ----------------------------