TeX source:

\bar{t}_{i j t}^{k}=\left(\frac{t_{i j t}^{k} t_{j i t}^{k}}{t_{i i t}^{k} t_{j j t}^{k}}\right)^{\frac{1}{2}}-1=\left(\frac{x_{i i t}^{k} x_{j j t}^{k}}{x_{i j t}^{k} x_{j i t}^{k}}\right)^{\frac{1}{2(s-1)}}-1