- https://www.heatdesign.ie/wp-content/uploads/ninja-forms/4/full-list-united-airlines-customer-service-contact-numbers-usa-comprehensive-guide.pdf
- https://community.bitsum.com/forum/index.php?topic=36997.0
- https://community.bitsum.com/forum/index.php?topic=37003.0
- https://community.bitsum.com/forum/index.php?topic=37001.0
- https://community.bitsum.com/forum/index.php?topic=37006.0
- https://community.bitsum.com/forum/index.php?topic=37010.0