https://w.atwiki.jp/airlineshelpcentre/pages/26.html

https://www.uncrownedgaming.com/blogs/blog/13-complete-guide-%F0%9D%95%B0%F0%9D%96%9D%F0%9D%96%95%F0%9D%96%8A%F0%9D%96%89%F0%9D%96%8E%F0%9D%96%86%E2%84%A2-customer-care%C2%AE-usa-contact-numbers-a-step-by-step-guide/

https://www.uncrownedgaming.com/forums/topic/5083-full-list-of-official-singapore-_-airlines%E2%84%A2%EF%B8%8F-contact-numbers%C2%AE%EF%B8%8F-in-the-usa-a-comprehensive-guide/

https://www.uncrownedgaming.com/forums/topic/5026-full-list-of-official-booking-com-contact-numbers-in-the-usa-a-complete-guide/

https://w.atwiki.jp/sadfasdf23/pages/22.html

https://metalarea.org/forum/index.php?showtopic=419111

https://metalarea.org/forum/index.php?showtopic=419109

https://www.goodreads.com/quotes/13727351-faqs-what-is-the-cheapest-day-to-buy-southwest-airlines

https://metalarea.org/forum/index.php?showtopic=419105

https://airlinesflight.zohodesk.com/portal/en/kb/articles/discount-how-to-get-discounts-on-alaska-flights