On the structure of families of immune, hyperimmune and hyperhyperimmune sets

The author studies the algebraic structures formed by $m$-degrees containing immune, hyperimmune and hyperhyperimmune sets. He shows that the family of all immune sets relative to $m$-reducibility forms a $c$-universal upper semilattice, the families of all hyperimmune and hyperhyperimmune sets do not form subsemilattices of the semilattice of all $m$-degrees, etc.
Bibliography: 9 titles.