The ownerNode property of the StyleSheet interface returns the node that associates this style sheet with the document. 
  This is usually an HTML <link> or <style> element, but can also return a processing instruction node in the case of <?xml-stylesheet ?>. 
 
<html lang="en">
  <head>
    <link rel="stylesheet" href="example.css" />
  </head>
  <body>
    <button onclick="alert(document.styleSheets[0].ownerNode)">
      Show example.css's ownerNode
    </button>
  </body>
</html>
// Displays "object HTMLLinkElement"
  
 For style sheets that are included by other style sheets, such as with @import, the value of this property is null.