1. The lattice of recursively enumerable sets (German);Herrmann,1978
2. On the lattice of recursively enumerable sets;Lachlan;Trans. Amer. Math. Soc.,1968
3. The elementary theory of recursively enumerable sets;Lachlan;Duke Math. J.,1968
4. r-maximal major subsets;Lerman;Israel J. Math.,1978
5. W. Maass, Characterization of recursively enumerable sets with supersets effectively isomorphic to all recursively enumerable sets, to appear