Always a fascinating area of research.
http://www.youtube.com/watch?v=bith2mIA6GQ, http://www.youtube.com/watch?v=LevvFKRjkSo
The Missing Secrets Of Nikola Tesla
http://www.youtube.com/watch?v=h5uiK_QnyrE
http://www.bibliotecapleyades.net/tesla/esp_tesla_35.htm,
http://www.henrymakow.com/teslas_flying_machine.html