Representations and projective representations Wigner's theorem

^ proved in detail in bargmann 1964.
^ de kerf & van groesen 1999, p. 344 stated not proved.
^ de kerf & van groesen 1999, p. 346 there error in formula in book.
^ weinberg 2002, p. 82
^ weinberg 2002, appendix b, chapter 2
^ bäurle & de kerf 1999, pp. 347–349
^ weinberg 2002, section 2.7.
^ straumann 2014

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