[1] "Internet Travel and Hotel Bookings," Statistic Brain (2016). https://www.statisticbrain.com/internet-travel-hotel-booking-statistics/
[2] "ASTA Releases Study on Time and Money Travel Agents Save Consumers," American Society of Travel Agents (June 2, 2016). https://www.asta.org/News/PRDetail.cfm?ItemNumber=14517&navItemNumber=539