diff --git a/public/iframed.html b/public/iframed.html
index 00c931e..cec4b17 100644
--- a/public/iframed.html
+++ b/public/iframed.html
@@ -22,242 +22,250 @@
     <title>Basic Example</title>
   </head>
   <body>
+    <p>Parent page is: <span id="parent-page"></span></p>
     <div id="container"></div>
     <script async
-      src="https://pay.google.com/gp/p/js/pay.js"
-      onload="onGooglePayLoaded()"></script>
+      src="https://pay.google.com/gp/p/js/pay.js"
+      onload="onGooglePayLoaded()"></script>
     <script>   
       /**
-       * Define the version of the Google Pay API referenced when creating your
-       * configuration
-       *
-       * @see {@link https://developers.google.com/pay/api/web/reference/request-objects#PaymentDataRequest|apiVersion in PaymentDataRequest}
-       */
+       * Define the version of the Google Pay API referenced when creating your
+       * configuration
+       *
+       * @see {@link https://developers.google.com/pay/api/web/reference/request-objects#PaymentDataRequest|apiVersion in PaymentDataRequest}
+       */
       const baseRequest = {
-        apiVersion: 2,
-        apiVersionMinor: 0
+        apiVersion: 2,
+        apiVersionMinor: 0
       };
 
       /**
-       * Card networks supported by your site and your gateway
-       *
-       * @see {@link https://developers.google.com/pay/api/web/reference/request-objects#CardParameters|CardParameters}
-       * @todo confirm card networks supported by your site and gateway
-       */
+       * Card networks supported by your site and your gateway
+       *
+       * @see {@link https://developers.google.com/pay/api/web/reference/request-objects#CardParameters|CardParameters}
+       * @todo confirm card networks supported by your site and gateway
+       */
       const allowedCardNetworks = ["AMEX", "DISCOVER", "INTERAC", "JCB", "MASTERCARD", "VISA"];
 
       /**
-       * Card authentication methods supported by your site and your gateway
-       *
-       * @see {@link https://developers.google.com/pay/api/web/reference/request-objects#CardParameters|CardParameters}
-       * @todo confirm your processor supports Android device tokens for your
-       * supported card networks
-       */
+       * Card authentication methods supported by your site and your gateway
+       *
+       * @see {@link https://developers.google.com/pay/api/web/reference/request-objects#CardParameters|CardParameters}
+       * @todo confirm your processor supports Android device tokens for your
+       * supported card networks
+       */
       const allowedCardAuthMethods = ["PAN_ONLY", "CRYPTOGRAM_3DS"];
 
       /**
-       * Identify your gateway and your site's gateway merchant identifier
-       *
-       * The Google Pay API response will return an encrypted payment method capable
-       * of being charged by a supported gateway after payer authorization
-       *
-       * @todo check with your gateway on the parameters to pass
-       * @see {@link https://developers.google.com/pay/api/web/reference/request-objects#gateway|PaymentMethodTokenizationSpecification}
-       */
+       * Identify your gateway and your site's gateway merchant identifier
+       *
+       * The Google Pay API response will return an encrypted payment method capable
+       * of being charged by a supported gateway after payer authorization
+       *
+       * @todo check with your gateway on the parameters to pass
+       * @see {@link https://developers.google.com/pay/api/web/reference/request-objects#gateway|PaymentMethodTokenizationSpecification}
+       */
       const tokenizationSpecification = {
-        type: 'PAYMENT_GATEWAY',
-        parameters: {
-          'gateway': 'example',
-          'gatewayMerchantId': 'exampleGatewayMerchantId'
-        }
+        type: 'PAYMENT_GATEWAY',
+        parameters: {
+          'gateway': 'example',
+          'gatewayMerchantId': 'exampleGatewayMerchantId'
+        }
       };
 
       /**
-       * Describe your site's support for the CARD payment method and its required
-       * fields
-       *
-       * @see {@link https://developers.google.com/pay/api/web/reference/request-objects#CardParameters|CardParameters}
-       */
+       * Describe your site's support for the CARD payment method and its required
+       * fields
+       *
+       * @see {@link https://developers.google.com/pay/api/web/reference/request-objects#CardParameters|CardParameters}
+       */
       const baseCardPaymentMethod = {
-        type: 'CARD',
-        parameters: {
-          allowedAuthMethods: allowedCardAuthMethods,
-          allowedCardNetworks: allowedCardNetworks
-        }
+        type: 'CARD',
+        parameters: {
+          allowedAuthMethods: allowedCardAuthMethods,
+          allowedCardNetworks: allowedCardNetworks
+        }
       };
 
       /**
-       * Describe your site's support for the CARD payment method including optional
-       * fields
-       *
-       * @see {@link https://developers.google.com/pay/api/web/reference/request-objects#CardParameters|CardParameters}
-       */
+       * Describe your site's support for the CARD payment method including optional
+       * fields
+       *
+       * @see {@link https://developers.google.com/pay/api/web/reference/request-objects#CardParameters|CardParameters}
+       */
       const cardPaymentMethod = Object.assign(
-        {},
-        baseCardPaymentMethod,
-        {
-          tokenizationSpecification: tokenizationSpecification
-        }
+        {},
+        baseCardPaymentMethod,
+        {
+          tokenizationSpecification: tokenizationSpecification
+        }
       );
 
       /**
-       * An initialized google.payments.api.PaymentsClient object or null if not yet set
-       *
-       * @see {@link getGooglePaymentsClient}
-       */
+       * An initialized google.payments.api.PaymentsClient object or null if not yet set
+       *
+       * @see {@link getGooglePaymentsClient}
+       */
       let paymentsClient = null;
 
       /**
-       * Configure your site's support for payment methods supported by the Google Pay
-       * API.
-       *
-       * Each member of allowedPaymentMethods should contain only the required fields,
-       * allowing reuse of this base request when determining a viewer's ability
-       * to pay and later requesting a supported payment method
-       *
-       * @returns {object} Google Pay API version, payment methods supported by the site
-       */
+       * Configure your site's support for payment methods supported by the Google Pay
+       * API.
+       *
+       * Each member of allowedPaymentMethods should contain only the required fields,
+       * allowing reuse of this base request when determining a viewer's ability
+       * to pay and later requesting a supported payment method
+       *
+       * @returns {object} Google Pay API version, payment methods supported by the site
+       */
       function getGoogleIsReadyToPayRequest() {
-        return Object.assign(
-            {},
-            baseRequest,
-            {
-              allowedPaymentMethods: [baseCardPaymentMethod]
-            }
-        );
+        return Object.assign(
+            {},
+            baseRequest,
+            {
+              allowedPaymentMethods: [baseCardPaymentMethod]
+            }
+        );
       }
 
       /**
-       * Configure support for the Google Pay API
-       *
-       * @see {@link https://developers.google.com/pay/api/web/reference/request-objects#PaymentDataRequest|PaymentDataRequest}
-       * @returns {object} PaymentDataRequest fields
-       */
+       * Configure support for the Google Pay API
+       *
+       * @see {@link https://developers.google.com/pay/api/web/reference/request-objects#PaymentDataRequest|PaymentDataRequest}
+       * @returns {object} PaymentDataRequest fields
+       */
       function getGooglePaymentDataRequest() {
-        const paymentDataRequest = Object.assign({}, baseRequest);
-        paymentDataRequest.allowedPaymentMethods = [cardPaymentMethod];
-        paymentDataRequest.transactionInfo = getGoogleTransactionInfo();
-        paymentDataRequest.merchantInfo = {
-          // @todo a merchant ID is available for a production environment after approval by Google
-          // See {@link https://developers.google.com/pay/api/web/guides/test-and-deploy/integration-checklist|Integration checklist}
-          // merchantId: '01234567890123456789',
-          merchantName: 'Example Merchant'
-        };
-        return paymentDataRequest;
+        const paymentDataRequest = Object.assign({}, baseRequest);
+        paymentDataRequest.allowedPaymentMethods = [cardPaymentMethod];
+        paymentDataRequest.transactionInfo = getGoogleTransactionInfo();
+        paymentDataRequest.merchantInfo = {
+          // @todo a merchant ID is available for a production environment after approval by Google
+          // See {@link https://developers.google.com/pay/api/web/guides/test-and-deploy/integration-checklist|Integration checklist}
+          // merchantId: '01234567890123456789',
+          merchantName: 'Example Merchant'
+        };
+        return paymentDataRequest;
       }
 
       /**
-       * Return an active PaymentsClient or initialize
-       *
-       * @see {@link https://developers.google.com/pay/api/web/reference/client#PaymentsClient|PaymentsClient constructor}
-       * @returns {google.payments.api.PaymentsClient} Google Pay API client
-       */
+       * Return an active PaymentsClient or initialize
+       *
+       * @see {@link https://developers.google.com/pay/api/web/reference/client#PaymentsClient|PaymentsClient constructor}
+       * @returns {google.payments.api.PaymentsClient} Google Pay API client
+       */
       function getGooglePaymentsClient() {
-        if ( paymentsClient === null ) {
-          paymentsClient = new google.payments.api.PaymentsClient({environment: 'TEST'});
-        }
-        return paymentsClient;
+        if ( paymentsClient === null ) {
+          paymentsClient = new google.payments.api.PaymentsClient({environment: 'TEST'});
+        }
+        return paymentsClient;
       }
 
       /**
-       * Initialize Google PaymentsClient after Google-hosted JavaScript has loaded
-       *
-       * Display a Google Pay payment button after confirmation of the viewer's
-       * ability to pay.
-       */
+       * Initialize Google PaymentsClient after Google-hosted JavaScript has loaded
+       *
+       * Display a Google Pay payment button after confirmation of the viewer's
+       * ability to pay.
+       */
       function onGooglePayLoaded() {
-        const paymentsClient = getGooglePaymentsClient();
-        paymentsClient.isReadyToPay(getGoogleIsReadyToPayRequest())
-            .then(function(response) {
-              if (response.result) {
-                addGooglePayButton();
-                // @todo prefetch payment data to improve performance after confirming site functionality
-                // prefetchGooglePaymentData();
-              }
-            })
-            .catch(function(err) {
-              // show error in developer console for debugging
-              console.error(err);
-            });
+
+        var parentUrl = (window.location != window.parent.location)
+            ? document.referrer
+            : document.location.href;
+
+        document.getElementById("parent-page").textContent = parentUrl;
+
+        const paymentsClient = getGooglePaymentsClient();
+        paymentsClient.isReadyToPay(getGoogleIsReadyToPayRequest())
+            .then(function(response) {
+              if (response.result) {
+                addGooglePayButton();
+                // @todo prefetch payment data to improve performance after confirming site functionality
+                // prefetchGooglePaymentData();
+              }
+            })
+            .catch(function(err) {
+              // show error in developer console for debugging
+              console.error(err);
+            });
       }
 
       /**
-       * Add a Google Pay purchase button alongside an existing checkout button
-       *
-       * @see {@link https://developers.google.com/pay/api/web/reference/request-objects#ButtonOptions|Button options}
-       * @see {@link https://developers.google.com/pay/api/web/guides/brand-guidelines|Google Pay brand guidelines}
-       */
+       * Add a Google Pay purchase button alongside an existing checkout button
+       *
+       * @see {@link https://developers.google.com/pay/api/web/reference/request-objects#ButtonOptions|Button options}
+       * @see {@link https://developers.google.com/pay/api/web/guides/brand-guidelines|Google Pay brand guidelines}
+       */
       function addGooglePayButton() {
-        const paymentsClient = getGooglePaymentsClient();
-        const button =
-            paymentsClient.createButton({onClick: onGooglePaymentButtonClicked});
-        document.getElementById('container').appendChild(button);
+        const paymentsClient = getGooglePaymentsClient();
+        const button =
+            paymentsClient.createButton({onClick: onGooglePaymentButtonClicked});
+        document.getElementById('container').appendChild(button);
       }
 
       /**
-       * Provide Google Pay API with a payment amount, currency, and amount status
-       *
-       * @see {@link https://developers.google.com/pay/api/web/reference/request-objects#TransactionInfo|TransactionInfo}
-       * @returns {object} transaction info, suitable for use as transactionInfo property of PaymentDataRequest
-       */
+       * Provide Google Pay API with a payment amount, currency, and amount status
+       *
+       * @see {@link https://developers.google.com/pay/api/web/reference/request-objects#TransactionInfo|TransactionInfo}
+       * @returns {object} transaction info, suitable for use as transactionInfo property of PaymentDataRequest
+       */
       function getGoogleTransactionInfo() {
-        return {
-          countryCode: 'US',
-          currencyCode: 'USD',
-          totalPriceStatus: 'FINAL',
-          // set to cart total
-          totalPrice: '1.00'
-        };
+        return {
+          countryCode: 'US',
+          currencyCode: 'USD',
+          totalPriceStatus: 'FINAL',
+          // set to cart total
+          totalPrice: '1.00'
+        };
       }
 
       /**
-       * Prefetch payment data to improve performance
-       *
-       * @see {@link https://developers.google.com/pay/api/web/reference/client#prefetchPaymentData|prefetchPaymentData()}
-       */
+       * Prefetch payment data to improve performance
+       *
+       * @see {@link https://developers.google.com/pay/api/web/reference/client#prefetchPaymentData|prefetchPaymentData()}
+       */
       function prefetchGooglePaymentData() {
-        const paymentDataRequest = getGooglePaymentDataRequest();
-        // transactionInfo must be set but does not affect cache
-        paymentDataRequest.transactionInfo = {
-          totalPriceStatus: 'NOT_CURRENTLY_KNOWN',
-          currencyCode: 'USD'
-        };
-        const paymentsClient = getGooglePaymentsClient();
-        paymentsClient.prefetchPaymentData(paymentDataRequest);
+        const paymentDataRequest = getGooglePaymentDataRequest();
+        // transactionInfo must be set but does not affect cache
+        paymentDataRequest.transactionInfo = {
+          totalPriceStatus: 'NOT_CURRENTLY_KNOWN',
+          currencyCode: 'USD'
+        };
+        const paymentsClient = getGooglePaymentsClient();
+        paymentsClient.prefetchPaymentData(paymentDataRequest);
       }
 
       /**
-       * Show Google Pay payment sheet when Google Pay payment button is clicked
-       */
+       * Show Google Pay payment sheet when Google Pay payment button is clicked
+       */
       function onGooglePaymentButtonClicked() {
-        const paymentDataRequest = getGooglePaymentDataRequest();
-        paymentDataRequest.transactionInfo = getGoogleTransactionInfo();
+        const paymentDataRequest = getGooglePaymentDataRequest();
+        paymentDataRequest.transactionInfo = getGoogleTransactionInfo();
 
-        const paymentsClient = getGooglePaymentsClient();
-        paymentsClient.loadPaymentData(paymentDataRequest)
-            .then(function(paymentData) {
-              // handle the response
-              processPayment(paymentData);
-            })
-            .catch(function(err) {
-              // show error in developer console for debugging
-              console.error(err);
+        const paymentsClient = getGooglePaymentsClient();
+        paymentsClient.loadPaymentData(paymentDataRequest)
+            .then(function(paymentData) {
+              // handle the response
+              processPayment(paymentData);
+            })
+            .catch(function(err) {
+              // show error in developer console for debugging
+              console.error(err);
               window.parent.postMessage("An error occured: " + error, "https://dmengelt.github.io");
-            });
+            });
       }
 
       /**
-       * Process payment data returned by the Google Pay API
-       *
-       * @param {object} paymentData response from Google Pay API after user approves payment
-       * @see {@link https://developers.google.com/pay/api/web/reference/response-objects#PaymentData|PaymentData object reference}
-       */
+       * Process payment data returned by the Google Pay API
+       *
+       * @param {object} paymentData response from Google Pay API after user approves payment
+       * @see {@link https://developers.google.com/pay/api/web/reference/response-objects#PaymentData|PaymentData object reference}
+       */
       function processPayment(paymentData) {
         console.log(paymentData);
         window.parent.postMessage("Success with card: " + paymentData.paymentMethodData.description, "https://dmengelt.github.io");
-        // show returned data in developer console for debugging        
-        // @todo pass payment token to your gateway to process payment
-        paymentToken = paymentData.paymentMethodData.tokenizationData.token;
+        // show returned data in developer console for debugging        
+        // @todo pass payment token to your gateway to process payment
+        paymentToken = paymentData.paymentMethodData.tokenizationData.token;
       }
     </script>
   </body>
