Paolini, Gianluca; Shelah, Saharon (2021). "Torsion-Free Abelian Groups are Borel Complete". arXiv:2102.12371 [math.LO].
doi.org
See for instance the introduction to Thomas, Simon (2003), "The classification problem for torsion-free abelian groups of finite rank", J. Am. Math. Soc., 16 (1): 233–258, doi:10.1090/S0894-0347-02-00409-5, Zbl1021.03043
See for instance the introduction to Thomas, Simon (2003), "The classification problem for torsion-free abelian groups of finite rank", J. Am. Math. Soc., 16 (1): 233–258, doi:10.1090/S0894-0347-02-00409-5, Zbl1021.03043