Lieber, S. I., Hendershott, M. C., Pattanaporkratana, A., & Maclennan, J. E. (2007). Self-organization of bouncing oil drops: Two-dimensional lattices and spinning clusters. Physical Review E, 75(5), 056308.

 

http://www.physics.emory.edu/~weeks/lab/papers/lieber-pre07-drop.pdf