1. Adyan, S.I.: Algorithmic unsolvability of problems of recognition of certain properties of groups. Dokl. Akad. Nauk SSSR (N.S.) 103, 533–535 (1955)
2. Adyan, S.I.: Unsolvability of some algorithmic problems in the theory of groups. Trudy Moskov. Mat. Obšč. 6, 231–298 (1957)
3. Agol, I.: The virtual Haken conjecture. Doc. Math. 18, 1045–1087 (2013) (with an appendix by Ian Agol, Daniel Groves and Jason Manning)
4. Bajpai, J.: Omnipotence of surface groups. Masters Thesis, McGill University (2007)
5. Baumslag, G., Boone, W.W., Neumann, B.H.: Some unsolvable problems about elements and subgroups of groups. Math. Scand. 7, 191–201 (1959)