C Muriel, JL Romero - Journal of Nonlinear Mathematical Physics, 2011 - World Scientific
We study the class of the ordinary differential equations of the form ẍ+ a2 (t, x) ẋ2+ a1 (t, x)
ẋ+ a0 (t, x)= 0, that admit v=∂ x as λ-symmetry for some λ= α (t, x) ẋ+ β (t, x). This class …