From: Approximate symmetries in nonlinear viscoelastic media
Case
Forms of f( w 0 x ) and λ( w 0 x )
Extensions of Approx L P
I
f( w 0 x )= f 0 e 2 p w 0 x
X 8 =x ∂ ∂ x +( w 0 +px) ∂ ∂ w 0 +s w 1 ∂ ∂ w 1
λ( w 0 x )= λ 0 e 1 + s p w 0 x
II
f( w 0 x )= f 0 ( w 0 x + q ) 2 p
X 8 =x ∂ ∂ x +[(1+p) w 0 +pqx] ∂ ∂ w 0 +s w 1 ∂ ∂ w 1
λ( w 0 x )= λ 0 ( w 0 x + q ) 1 + s p − 1