1. Yu. I. Merzlyakov,Rational Groups [in Russian], 2nd edn., Nauka, Moscow (1987).
2. V. G. Bardakov, “Toward a theory of braid groups”,Mat. Sb.,183, No. 6, 3–42 (1992).
3. A. H. Rhemtulla, “A problem of bounded expressibility in free products”,Proc. Cambridge Phil. Soc.,64, No. 3, 573–584 (1969).
4. A. H. Rhemtulla, “Commutators of certain finitely generated solvable groups”,Can. J. Math.,21, No. 5, 1160–1164 (1969).
5. The Kourovka Notebook: Unsolved Problems in Group Theory, 12th edn., Novosibirsk (1992).