docs: public static double volatilityConversionLognormalATMtoNormalATM(double forward, double displacement, double maturity, double lognormalVolatiltiy) {
  		double x = lognormalVolatiltiy * Math.sqrt(maturity / 8);
  		double y = org.apache.commons.math3.special.Erf.erf(x);
  		double normalVol = Math.sqrt(2*Math.PI / maturity) * (forward+displacement) * y;
  
  		return normalVol;
  	}