P. Carrasco et Am. Cegarra, CENTRAL EXTENSIONS OF CATEGORICAL GROUPS BY BRAIDED CATEGORICAL GROUPS, Comptes rendus de l'Academie des sciences. Serie 1, Mathematique, 321(5), 1995, pp. 527-530
This goes accompanied with another Note [2]. introduction of the set o
f equivalence classes of central extensions of a categorical group by
a braided categorical group. Introduction of the cohomology set of a c
ategorical group with coefficients in a braided categorical group. Coh
omology classification theorem Homotopy classification theorem.