A similar relationship can be found for the volatility constant H v , 2 , M p x , by remembering that H v p x = 1 / H s x p and that, both being positive real numbers, ln ⁡ ⁡ H s x p = − − ln ⁡ ⁡ ( 1 / H s x p ) = − − ln ⁡ ⁡ H v p x , thus: