parcial.html

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="utf-8">
        <title>D3 Page Template</title>
        <link rel="stylesheet" type="text/css" href="parcial.css">
    
       
    
        <script type="text/javascript" src="d3.v3.min.js"></script>
    </head>
    <body id="cascadeRendering">
<button id="zoom_in">+</button>
<button id="zoom_out">-</button>

        <script type="text/javascript" src="parcial.js"></script>
       
    </body>
</html>