| https://12313.zohodesk.com/portal/en/kb/articles/today-frontier-503-c%C3%B3mo-hablo-con-alguien-en-frontier |
| https://sites.google.com/view/frontierayudaelsalvador/ |
| https://www.zupyak.com/p/4704626 |
| https://www.goodreads.com/quotes/15031127-c-mo-puedo-hablar-con-un-agente-de-united-airlines-usa |
| https://www.zupyak.com/p/4704677 |
