def feed_url(format = :rss20)
    blog.url_for(:controller => 'xml', :action => 'feed', :type => 'article', :format => format, :id => id)
  end

  def self.find_by_permalink(year=nil, month=nil, day=nil, title=nil)
    if self.blog.seopermalinks == 0
      unless month
        case year
        when Hash
          year, month, day, title = date_from(year)
        when Array
          year, month, day, title = year
        end
      end
      from, to = self.time_delta(year, month, day)
      returning(find_published(:first,
                               :conditions => ['permalink = ? AND ' +
                                               'published_at BETWEEN ? AND ?',
                                               title, from, to ])) do |res|
        if res.nil?
          raise ActiveRecord::RecordNotFound
        end
      end
    else
      returning(find_published(:first, 
        :conditions => ['permalink = ? ' , title])) do |res|
        if res.nil?
          raise ActiveRecord::RecordNotFound
        end
      end
    end
  end