joining Table Zend_Db_Table_Abstract and getting values

hi,
I am trying to join two tables
my blog_post table has field 'post_category' Which contains number and that is related to my
'blog_category' table with the text, its like id-value pair

        blog_post    Blog_category  
              '1'             'general'

But I cannot join table and fetch related data.
Below is the information, your help is highly appreciated, thanks

I have two tables in a database

        -> Blog_posts ('id' ,'post_category','post_title','post_content')
        -> Blog_category ('term_id','name')
       

My model class is as below

class Blog extends Zend_Db_Table_Abstract {
    protected $_name = 'blog_posts';
        protected $_dependentTables = array('Blog_Category');        

}

class Blog_Category extends Zend_Db_Table_Abstract {
    protected $_name = 'blog_category';
        protected $_referenceMap = array(
                                'Blog' => array(
                                        'columns' => array('term_id'),
                                        'refTableClass' => 'blog',
                                        'refColumns' => array('post_category')
                                        )
                        );
}




My controller is as below

 $blog1 = new Blog();
$row = $blog1->fetchRow('id = 1');
$this->view->cat = $row->findDependentRowset('Blog_Category');


but I get this error message
 
Fatal error: Uncaught exception 'Zend_Db_Table_Exception'
with message 'No reference from table Blog_Category to table Blog'……
…………………………………… Zend_Db_Table_Abstract->getReference('Blog', NULL) #1


thanks for your help