1. INTRODUCTION

2. OBSERVATIONS AND DATA REDUCTION
2.1. Spitzer/IRS
2.2. IRTF/SpeX
2.3. Ancillary Photometry

3. BASIC CHARACTERISTICS OF THE STARS
3.2. Extinction Correction
3.3. Spectral Energy Distributions
3.4. Stellar Luminosity and Stellar Mass

4. DISK PROPERTIES
4.1. Spectral Index
4.2. Parameters of the Degree of Dust Processing
4.3. Disk Classification
4.4. Mass Accretion Rates

5. COMPARISON TO DISKS IN TAURUS
5.1. Index from 5-14 μm spectrum: Trapezium, ONC, L1641 and Taurus
5.2. Disk and Dust Processing Indicators from Full IRS Spectra: ONC, L1641 and Taurus
5.3. Median Spectra

6. ENVIRONMENTAL EFFECTS AND EVOLUTIONARY FEATURES OF THE OUTER DISKS

7. SUMMARY AND CONCLUSION