$(document).ready(function(){
	$("a.slider").nextAll(".abstract").hide();
	$("a.slider").click(function(){
		$(this).nextAll(".abstract").slideToggle('normal');
		
		 /*Here comes the part, that exchanges the plus and minus image: */
		if ($(this).children("img").attr('src') == "images/plus.png"){
			$(this).children("img").attr('src' ,"images/minus.png");
			}
		else {
			$(this).children("img").attr('src', "images/plus.png");
			}
	});
});