A common ansatz for computing solutions is the difference property, R ( u , u ′ ) = R ( u − − u ′ ) , where R depends only on a single (additive) parameter. Equivalently, taking logarithms, we may choose the parametrization R ( u , u ′ ) = R ( u / u ′ ) , in which case R is said to depend on a multiplicative parameter. In those cases, we may reduce the YBE to two free parameters in a form that facilitates computations: