| https://regions-and-cities.europa.eu/sites/default/files/webform/multimedia_center/54315/what-is-the-cheapest-day-to-fly-on-copa-airlines_%28book-now-24_7.pdf |
| https://regions-and-cities.europa.eu/sites/default/files/webform/multimedia_center/54315/what-is-the-cheapest-day-to-fly-lufthansa_-%28booking-guide-24_7-%281.pdf |
| https://www.goodreads.com/quotes/13091061-what-is-the-cheapest-day-to-fly-lufthansa-booking-guide |
| https://regions-and-cities.europa.eu/sites/default/files/webform/multimedia_center/54315/how-do-i-get-a-response-from-american_%281-800-american-1.pdf |
| https://regions-and-cities.europa.eu/sites/default/files/webform/multimedia_center/54315/how-do-i-get-a-response-from-american_how-do-i-get——————-to-respond_-%5Bfaq%5D.pdf |
