https://www.wyomilitary.wyo.gov/wp-content/uploads/formidable/14/e-x-p-e-dia-usa-customer-service-full-step-by-step-guide.pdf
https://education.aaaai.org/sites/default/files/webform/complete-list-of-official-expedia-customer-contact-numbers-in-the-usa-the-ultimate-detailed-guide.pdf
https://chandoo.org/forum/threads/way-to-call-to-live-agent-at-american-airlines-helpdesk-support.60043/
https://educativ.net/forums/topic/38837-complete-list-of-united-airlines-customer-support-numbers-in-the-usa-%E2%80%93-2025-official-guide/
https://educativ.net/forums/topic/38843-complete-list-of-official%E2%84%A2-bookingcom%C2%AE-contact-numbers-in-the-usa-%E2%80%93-2025-full-guide/
https://updatesonproperty.com/full-list-of-expedia%EF%B8%8F-customer-service-contact-numbers-in-the-usa-a-step-by-step-guide
https://educativ.net/forums/topic/38718-complete-list-of-frontier-airlines-customer-service-numbers-in-the-usa-%E2%80%93-2025-official-guide/