+ Double_t fSumX; // weighted summ of X
+ Double_t fSumX2; // weighted summ of X**2
+ Double_t fSumX3; // weighted summ of X**3
+ Double_t fSumX4; // weighted summ of X**4
+ Double_t fSumY; // as X
+ Double_t fSumYX; // summ of X*Y
+ Double_t fSumYX2; // summ of X**2*Y
+ Double_t fSumZ; // summ of Z
+ Double_t fSumZX; // summ of Z*X
+ Double_t fSumZX2; // summ of Z*X**2