Не работает slick слайдер, почему?

$('.modal1').click(function() {
    	$('#modalwindow').arcticmodal()
    });

$('.single-item').slick();

<link rel="stylesheet" href="css/simple.css">
	<link rel="stylesheet" href="css/jquery.arcticmodal-0.3.css">
	<link rel="stylesheet" href="css/bootstrap.min.css">
	<link rel="stylesheet" href="css/slick-theme.css">
	<link rel="stylesheet" href="css/slick.css">
	<link rel="stylesheet" href="css/style.css">
<section id="fourth">
		<div class="container">
			<div class="row">
				<div class="col-lg-12 text-center">
					<h2 class="fourth_title">Beautiful Interface</h2>
					<p class="fourth_title_down">Landing Screen</p>
				</div>
				<div class="row">
					<div class="col-lg-12 text-center">
						<div class="single-item">
							<div><img src="img/1.png" alt=""></div>
							<div><img src="img/2.png" alt=""></div>
							<div><img src="img/3.png" alt=""></div>
							<div><img src="img/4.png" alt=""></div>
						</div>
					</div>
				</div>
			</div>
		</div>
	</section>
	<script src="js/jquery.js"></script>
	<script src="js/bootstrap.min.js"></script>
	<script src="js/jquery.arcticmodal-0.3.min.js"></script>
	<script src="js/slick.min.js"></script>
	<script src="js/slick.js"></script>
	<script src="js/main.js"></script>