Before revision: The analytical tractability of affine (short rate) models, such as the Vasi\v{c and the Cox-Ingersoll-Ross models, has made them a popular choice for modelling the dynamics of interest rates.
After revision: The analytical tractability of affine (short rate) models, such as the Vasicek and the Cox-Ingersoll-Ross models, has made them a popular choice for modelling the dynamics of interest rates.