Core decision problems for two-relator groups
Decide the word problem, conjugacy problem, and isomorphism problem for the class of finitely presented groups with two defining relations.
References
The word problem, conjugacy problem, and isomorphism problem are all open for two-relator groups.
— The theory of one-relator groups: history and recent progress
(2501.18306 - Linton et al., 30 Jan 2025) in Subsection 8.3 (Two-relator groups)