1. INTRODUCTION  
2. OBSERVATION  
2.1. AZT-22 1.5m Telescope of Maidanak Astronomical Observatory  
2.2. Kuiper 61” Telescope of Steward Observatory  
2.3. The Consistency and Completeness of the Photometric Data  
3. PHOTOMETRIC DIAGRAMS  
4. HERTZSPRUNG-RUSSELL DIAGRAM  
5. INITIAL MASS FUNCTION  
6. DISCUSSIONS ON THE AGE SPREAD OF PMS STARS  
7. SUMMARY