1 INTRODUCTION  
2 SAMPLE SELECTION AND DATA PREPARATION  
3 TIMING ANALYSIS  
3.1 Approach and Implementation  
3.2 Candidate periodic signals  
4 X-RAY SPECTRAL PROPERTIES  
5 CLASSIFYING THE PERIODIC SOURCES  
5.1 𝜔 Cen  
5.2 M 62  
5.3 NGC 6397  
5.4 Terzan 5  
5.5 M 28  
5.6 NGC 6752  
6 DISCUSSION  
6.1 CV population in individual GCs  
6.2 The global properties of GC CVs  
7 SUMMARY