1. Levi, I., Normal semigroups of one-to-one transformations,Proc. of Edinburg. Math. Soc., to appear.
2. Levi, I. and W. Williams, Normal semigroups of partial one-to-one transformations I,Lattices, Semigrous, and Universal Algebra, Plenum, 1990.
3. Levi, I. and S. Seif, On Congruences of -normal semigroups,Semigroup Forum, to appear.
4. Levi, I., Injective Endomorphisms of -normal semigroups: Finite Defects, submitted.
5. Levi, I., Injective Endomorphisms of -normal semigroups: Infinite Defects, submitted.