1. INTRODUCTION  
2. SED MODEL  
2.2. M dwarf model  
3. IMAGING DATA  
3.1. Broadband data  
3.2. Medium-band data  
4. HIGH-REDSHIFT QUASAR SELECTION  
4.1. Broadband color selection criteria  
5.2. Spectroscopic identification  
6. LUMINOSITY FUNCTION AND IMPLICATION FOR REIONIZATION  
7. SUMMARY