Physical states and BRST operators for higher-spin W strings Yu-Xiao Liu, Shao-Wen Wei, Li-Jie Zhang and Ji-Rong Ren Eur. Phys. J. C, 60 4 (2009) 675-684 Published online: 28 February 2009 DOI: 10.1140/epjc/s10052-009-0958-6