210 Appendix E Standard pQCD Results E.1 Light Cone Coordinates E.1.1 Definitions; Identities A four-vector is not bold-faced (e.g. p , k ), a three-vector is bold-faced with a vector symbol (e.g. ⃗ p , ⃗ k ), and a transverse two-vector is bold-faced with- out a vector symbol (e.g. p , k ). Minkowski four-vectors are written with parentheses, (); light-cone four-vectors with brackets, []. We will use non-symmetrized lightcone coordinates: p = ( p $^{0}$, p $^{z}$, p ) = [ p $^{+}$, p $^{−}$, p ] . (E.1) p + = p 0 + p z (E.2) p − = p 0 − p z (E.3) p = p . (E.4)