Chung Probability Pdf Review

$$ f_{\text{Chung}}(x) = \frac{1}{2\sqrt{2\pi}}\frac{1}{x^{\frac{3}{2}}} \exp\left( - \frac{1}{2x} \right) $$ for $x>0$

References: Chung, K. L., & Fuchs, W. H. J. (1946). On the law of the iterated logarithm. Proceedings of the American Mathematical Society, 2(5), 312-319. chung probability pdf

Could you give more explanation on chung assumputions Or Provide Assumuption on chung distiribution 0$ References: Chung