Further generalizing the Laplace–Runge–Lenz vector to other potentials and special relativity, the most general form can be written as A = ( ∂ ∂ ξ ξ ∂ ∂ u ) ( p × × L ) + [ ξ ξ − − u ( ∂ ∂ ξ ξ ∂ ∂ u ) ] L 2 r ^ ^ ,