1. INTRODUCTION

2. THE MASIV SAMPLE

3. REVIEW OF THE LITERATURE
3.1. Redshifts from the Literature
3.2. Optical identification

4. SPECTROSCOPIC FOLLOW-UP
4.1. Classification Scheme
4.2. Summary of the spectroscopic follow-up
4.3. RESULTS AND SAMPLE PROPERTIES
4.4. MASIV and other Blazar Surveys

5. DISCUSSION
5.1. Dependence of ISS on 5 GHz flux density and optical spectral type
5.2. ISS versus Redshift
5.3. ISS and Radio Power
5.4. ISS and Optical Brightness
5.5. Modeling the ISS dependence on Redshift

6. SUMMARY