1. Introduction
2. Data Sample and Treatment
2.1. Abundance Analysis
2.2. Sample Selection
3. Results
3.1. A Quality Control Test on the Na-O Anti-correlation
3.2. Mg-Al Anti-correlation
4. Discussion
4.1. Comparison with Field Stars
4.2. Mg-Al Anti-correlation Extension
4.3. Low-Mg in Extragalactic GCs
5. Summary and Conclusions