Statistics — multiple and partial correlation coefficients

If $R_{i.jk}$ represents multiple correlation coefficient, $r_{ij}$ represents simple correlation coefficient and $\sigma_i$ represents standard deviation of variate $X_i$ for a multivariate data set, then consider the following statements:

I. $R_{1.23}^2=\sigma_1^2\sigma_2^2(1-r_{12}^2)(1-r_{13})^2$

II. $R_{1.23}^2\ge r_{12}^2$

III. $R_{1.23}^2\ge r_{13.2}^2$

Which of the statements given above are correct?