In this paper, we prove, for a space X, the following are equivalent: 1. X is a D1 space with a regular-Gδ-diagonal, 2. X is a D2 space with a regular-Gδ-diagonal, 3. X is a semi-developable space with Gδ (3) -diagonal, 4. X is a D1-space with a Gδ(3)-diagonal, 5. X is a D2 -space with a Gδ(3)-diagonal, 6. X is a q, -space with a G*δ (2)-diagonal, 7. X is a semi-developable space with G*δ (2)-diagonal, 8. X is a semimetrizable, c-stratifiable space, 9. X is a c-Nagata -space, 10. X is a K-semimetrizable.

In this paper, we prove, for a space X, the following are equivalent: 1. X is a D1 space with a regular-Gδ-diagonal, 2. X is a D2 space with a regular-Gδ-diagonal, 3. X is a semi-developable space with Gδ (3) -diagonal, 4. X is a D1-space with a Gδ(3)-diagonal, 5. X is a D2 -space with a Gδ...