Notes on Essentially Finitely Indecomposable Nonthick Primary Abelian Groups

A note on essential finite indecomposability and thickness in primary abelian groups

“…Clearly each thick group is efi (otherwise, consider the projection onto an unbounded Σ-cyclic summand), while the converse is not true (see, e.g., [6] and [5]). Nevertheless, these two classes share some interesting properties; for instance in [2] it was proved that G is efi if and only if G/p ω G has this property.…”