1. A. G. Pinus, "On the Cartesian product operation," Izv. Vyssh. Uchebn. Zaved., Mat., No. 8, 51–53 (1983).
2. J. Adamek, V. Koubek, and N. Trnkova, "Sums of Boolean spaces represent every group," Pac. J. Math.,61, No. 1, 1–6 (1975).
3. W. Hanf, "On some fundamental problems concerning isomorphism of Boolean algebras," Math. Scand.,5, No. 2, 205–217 (1957).
4. A. L. S. Corner, "On a conjecture of Pierce concerning direct decompositions of Abelian groups," in: Proc. Colloq. Abelian Groups, Tihany, September, 1963, L. Fuchs and E. T. Schmidt (eds.), Hungarian Academy of Sciences, Budapest (1964), pp. 43–48.
5. B. Jonsson, "On isomorphism types of groups and other algebraic systems," Math. Scand.,5, 224–229 (1957).