Non-amenable finitely presented torsion-by-cyclic groups. Ol'shanskij, A.Yu.; Sapir, M.V. — 2001 Electronic Research Announcements of the American Mathematical Society [electronic only]
The conjugacy problem for groups, and Higman embeddings. Ol'shanskii, A.Yu.; Sapir, M.V. — 2003 Electronic Research Announcements of the American Mathematical Society [electronic only]