According to Landau-Lifschitz's Course of Theoretical Physics the electric current density is in Gaussian units: j e = q 2 m [ ( Ψ Ψ ∗ ∗ p ^ ^ Ψ Ψ − − Ψ Ψ p ^ ^ Ψ Ψ ∗ ∗ ) − − 2 q c A | Ψ Ψ | 2 ] + μ μ S c s ℏ ℏ ∇ ∇ × × ( Ψ Ψ ∗ ∗ S Ψ Ψ )