Central twisted transformation groups and group C*-algebras of central group expansions Siegfried EchterhoffDana Williams 46L5522D2543A6522D05crossed productstwisted crossed productsMoore cohomologygroup $C^*$-algebrascentral group extensions Indiana University Mathematics Journal 2002 text pdf 10.1512/iumj.2002.51.2193 10.1512/iumj.2002.51.2193 en Indiana Univ. Math. J. 51 (2002) 1277 - 1304 state-of-the-art mathematics http://iumj.org/access/