1. INTRODUCTION  
2. SOURCE SAMPLE  
3. OBSERVATIONS AND DATA REDUCTION  
4. RESULTS  
4.1. Continuum Determination  
4.2. Absorption Features  
5. CONSTRAINING THE ORIGIN OF THE 5–8 µm ABSORPTION FEATURES  
5.1. Absorption by Known Species  
5.2. Correlations  
6. DISCUSSION  
6.2. Potential Carrier(s) of Component C5  
6.3. Potential Carrier(s) of Component C2  
6.4. Astrochemical Implications  
7. CONCLUSIONS AND FUTURE WORK