1. Introduction

2. Overview of the new method and the data
2.1. Method
2.3. Caveats on photo-ionization due to non-AGN sources

3. Dust in AGNs and AGN power indicator
3.1. Extinction in AGNs
3.2. A new indicator of AGN power and comparisons with X-ray power

4. Nature of the Oxygen-excess objects: AGN activities and the host galaxy properties
4.2. Dependence of LINERs and Seyferts on host galaxies

5. Summary and Discussion