자세한 설명
https://sciencebasedlife.wordpress.com/2012/11/01/the-kopp-etchells-effect/
The Kopp-Etchells Effect Explained
Descending into a drab, unnamed war zone, the helicopter is familiar sight. As it kicks up dust and s...
자세한 설명
https://sciencebasedlife.wordpress.com/2012/11/01/the-kopp-etchells-effect/