1 INTRODUCTION
2 OBSERVATIONS AND DATA REDUCTION
2.1 Medium-resolution data
2.2 Radial velocity measurements
3 CHEMICAL ANALYSIS
3.1 Stellar Parameters
3.2 Abundance measurements
3.3 NLTE Calculations
3.4 Comments on individual elements
3.5 Carbon and Nitrogen
3.6 Consistency check on atmospheric parameters
4 RESULTS
4.1 Constraints on the C and N abundances
4.2 Overall chemical pattern
4.3 Comparison with previous spectroscopic studies
4.4 Model Predictions for UMP progenitor supernovae
5 CONCLUSIONS