1. INTRODUCTION  
2. PRACTICAL CONSIDERATIONS  
3. TARGET SELECTION AND OBSERVATIONS  
4. STELLAR MODELS  
5. MEASUREMENT OF $N(\mathrm{H\Omega_{I})}$  
6. NEW MEASUREMENTS OF $N(\mathrm{D~I})$  
7. N ( H i ) AND D/H RESULTS  
8. MEASUREMENT OF METAL ABUNDANCES  
9. CORRELATION WITH DEPLETIONS OF HEAVY ELEMENTS  
10. DISCUSSION  
11. SUMMARY  