This proof uses two-parameter Borel-Cantelli lemma and maximum inequality of Brownian sheet, which shows more characteristic in probability way. And the process of the proof is similar to that of single-parameter Brownian motion.

• 该方法使用两参数Borell-Cantelli引理和布朗单的最大值不等式，证明较有概率论方法特点，并且类似于单指标布朗运动的情形。