By courtesy of:
Virgil Percec, Andres E. Dulcey, Venkatachalapathy S. K. Balagurusamy, Yoshiko Miura, Jan Smidrkal, Mihai Peterca, Sami Nummelin, Ulrica Edlund, Steven D. Hudson, Paul A. Heiney, Hu Duan, Sergei N. Magonov & Sergei A. Vinogradov
Nature, 2004, 430, 764