Answering some queries of Weiss, we prove that the free product and amenable extensions of sofic groups are sofic as well, and give an example of a finitely generated sofic group that is not residually amenable.
On the cyclic subgroup separability of free products of two groups with amalgamated subgroup
Linear programming and the intersection of free subgroups in free products of groups
On the intersection of free subgroups in free products of groups
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