$(document).ready(function(){
	$(".article_ref").mouseover(function(){
		
		var $secondary  = $(this).children(".secondary");
		var $primary    = $(this).children(".primary");
		
		if ($secondary.length > 0){
			$secondary.removeClass("hidden");
			$primary.addClass("hidden");
		}		
    });
	$(".article_ref").mouseout(function(){
		
		var $secondary  = $(this).children(".secondary");
		var $primary    = $(this).children(".primary");
		
		if ($secondary.length > 0){
			$secondary.addClass("hidden");
			$primary.removeClass("hidden");
		}		
    });
});