“…It has been known that the relativistic effect due to transversal motions of quarks [15,16,17,18,19] and the sea content of the nucleon [20] play important roles to understand the proton spin problem. A number of models concerning the sea content of the nucleon, such as the baryon-meson fluctuation model [21] and the chiral quark model [22,23], not only play significant roles to understand the proton spin structure [20,21,24], but also show their remarkable significance to explain the flavor asymmetry of the nucleon sea [21,25,26,27] reported by the NMC collaboration [28,29]. More interestingly, the baryon-meson fluctuation model and the chiral quark model have been also found to produce a strange-antistrange asymmetry of the nucleon, and such strangeness asymmetry with natural model estimations [30,31,32] can explain the NuTeV anomaly [33,34] of the deviation of the NuTeV measured value of weak mixing angle compared with other measurements.…”