J. D. Jackson (1975) [1962]. "Chapter 11". Classical Electrodynamics (2nd ed.). John Wiley & Sons. pp. 556–557. ISBN0-471-43132-X. Jackson's notation: S (spin in F, lab frame), s (spin in F′, rest frame of particle), S0 (timelike component in lab frame), S′0 = 0 (timelike component in rest frame of particle), no symbol for 4-spin as a 4-vector