We first characterize $tau$-complemented modules with relative (pre)-covers. We also introduce an extending module relative to $tau$-pure submodules on a hereditary torsion theory $tau$ and give its relationship with $tau$-complemented modules.

let s be a locally compact foundation semigroup with identity and                          be its semigroup algebra. let x be a weak*-closed left translation invariant subspace of    in this paper, we prove that  x  is invariantly  complemented in   if and  only if  the left ideal  of    has a bounded approximate identity. we also prove that a foundation semigroup with identity s is left amenab...

Rosenthal [R] introduced the Lp space Xp in 1971. Among its interesting properties are that it contains and is contained in isomorphs of lp ⊕ l2, but is not isomorphic to a complemented subspace of lp⊕ l2. These properties have made Xp rather resistant to standard approaches to classifying its complemented subspaces. For example it was first proved that Xp was primary in [JO2] where the device ...