Perturbative and nonperturbative contributions to the strange quark asymmetry in the nucleon Guan-Qiu Feng, Fu-Guang Cao, Xin-Heng Guo and A. I. Signal Eur. Phys. J. C, 72 12 (2012) 2250 Published online: 01 December 2012 DOI: 10.1140/epjc/s10052-012-2250-4