1 INTRODUCTION

2 BASS: SAMPLE AND DATA  
2.1 X-ray data  
2.2 Optical data, black hole masses and Eddington ratio  

3 THE RELATION BETWEEN THE CUTOFF ENERGY AND THE PHYSICAL PROPERTIES OF THE ACCRETING SMBH

4 AGN IN THE TEMPERATURE–COMPACTNESS PARAMETER SPACE

5 THE PLASMA OPTICAL DEPTH AND ITS RELATION WITH THE ACCRETION PROPERTIES OF AGN

6 THE TEMPERATURE-COMPACTNESS PLANE AND THE $\Gamma-\lambda_{\mathrm{EDD}}$ CORRELATION  

7 SUMMARY AND CONCLUSION