function selectVoorstelling(id){ 
  if (document.referrer&&document.referrer!="") {
    // Get referer URL:
    var referer = document.referrer;
    // Strip last "/":
    if (referer.substring([referer.length-1])=="/") referer = referer.substring(0,referer.length-1);
    // Split URL into array on "/"
    var refererSegments = referer.split("/");
    var len = refererSegments.length;
    // Check 1st part of path [3] and/or domainname [2] and check if there is a subpage (length > 3)
    if (refererSegments[3]=="voorstellingen" && (len>3)) {
      // Voorstelling is last part of the path, so len - 1
      var voorstelling = refererSegments[len-1];
      // Check if input-element with the chosen id exists in DOM
      if (document.getElementById(id)) {
        // Set voorstelling as input value
        document.getElementById(id).value = voorstelling;
      }
    }
  }
}