Before revision: Extrinsic noise-induced transitions  have been largely investigated in a variety of chemical and physicalsystems. The key properties that make these systems mathematically tractable is that the noise appears linearly in the dynamical equations  and it is assumed Gaussian and white.
After revision: Extrinsic noise-induced transitions have been largely investigated in a variety of chemical , physical, and biological systems. In the standard approach in physical and chemical systems, the key properties that make these systems mathematically tractable is that the noise appears linearly in the dynamical equations and it is assumed Gaussian and white.