1. “The history of hot air balloon.” http://messel.emse.fr/∼tdaurat/montgolf/haballoon.html
2. G Bradshaw “The tale of the airplane.” http://www.wam.umd.edu/∼stwright/WrBr/taleplane.html
3. Ibid
4. “Space health requirements: The challenges,”;Czerwinski;Life Support and Biosphere Science,May 1998
5. “Flying high: The history of flight attendants.” http://airtravel.about.com/travel/airtravel/library/weekly/aa080899.htm