nopCommerce site: https://www.nopcommerce.com
Listing on nopCommerce "extensions and themes" catalog: https://www.nopcommerce.com/qualpay-payment-gateway
Qualpay site: https://www.qualpay.com/
Qualpay Payment Gateway documentation: https://www.qualpay.com/download/qppg/Payment_Gateway_Specification_V1.4.pdf