Weller, A., Spong, D. A., Jaenicke, R., Lazaros, A., Penningsfeld, F. P., Sattler, S., et al. (1994). Neutral beam driven global Alfvén eigenmodes in the Wendelstein W7-AS stellarator. Physical Review Letters, 72(8), 1220-1223. doi:10.1103/PhysRevLett.72.1220.