HWMonitor, RealTemp & Core temp: these 3 softwares are showing different core temps. Why?? which one is correct??

Click image for larger version. 

Name:	cpu.JPG 
Views:	13 
Size:	95.5 KB 
ID:	24863

- - - Updated - - -

& @Full Load

Real Temp v3.70 : 55C
Core Temp v1.0 RC3 : 60C
Open Hardware Monitor : 60C
CPUID HWMonitor : 65C