BachelierImpvol         Calculate Bachelier model implied volatility
BachelierPrice          Calculate Bachelier model option price
BlackScholesImpvol      Calculate Black-Scholes implied volatility
BlackScholesPrice       Calculate Black-Scholes option price
CevMassZero             Calculate the mass at zero under the CEV model
CevPrice                Calculate the constant elasticity of variance
                        (CEV) model option price
Nsvh1Choi2019           Calculate the option price under the NSVh model
                        with lambda=1 (Choi et al. 2019)
SabrHagan2002           Calculate the equivalent BS volatility (Hagan
                        et al. 2002) for the Stochatic-Alpha-Beta-Rho
                        (SABR) model
SpreadBachelier         Spread option under the Bachelier model
SpreadBjerksund2014     Spread option pricing method by Bjerksund &
                        Stensland (2014)
SpreadKirk              Kirk's approximation for spread option
SwitchMargrabe          Margrabe's formula for exhange option price
