- K-D

De Concini, Corrado; Kac, Victor G. Representations of quantum groups at roots of 1. Operator algebras, unitary representations, enveloping algebras, and invariant theory (Paris, 1989), 471--506, Progr. Math., 92, Birkhäuser Boston, Boston, MA, 1990.

- Dr1

V. G. Drinfeld, "On Almost Cocommutative Hopf Algebras," Leningrad Mathematical Journal, Vol. 1, No. 2, 1990, pp. 321-342.

- Dr2

V. G. Drinfeld, "On quasitriangular quasi-Hopf algebras and on a~group that is closely connected with $\mathrm{Gal}(\overline{\mathbb Q}/\mathbb Q)$," Leningrad Mathematical Journal, 1991, 2:4, 829–860.