  Using the iterative solution of Boltzmann equation in the relaxation-time
approximation, the derivation of a third-order evolution equation for shear
stress tensor is presented. To this end we first derive the expression for
viscous corrections to the phase-space distribution function, $f(x,p)$, up to
second-order in derivative expansion. The expression for $\delta f(x,p)$
obtained in this method does not lead to violation of the experimentally
observed $1/\sqrt{m_T}$ scaling of the femtoscopic radii, as opposed to the
widely used Grad's 14-moment approximation. Subsequently, we present the
derivation of a third-order viscous evolution equation and demonstrate the
significance of this derivation within one-dimensional scaling expansion. We
show that results obtained using third-order evolution equations are in
excellent accordance with the exact solution of Boltzmann equation as well as
with transport results.
