feat: added reference for CRx MSRs

docs/re.md

@@ -177,6 +177,8 @@ to either be set or cleared (still quite vague for now) so that a call to
 > IA32_VMX_CR4_FIXED0 and IA32_VMX_CR4_FIXED1 (see Appendix A.8)._
 
 
+Useful reference[^6]
+
 ```c
 // Function to check if VMXON can be executed without a protection exception
 int check_vmxon_conditions() {
@@ -237,6 +239,8 @@ int check_vmxon_conditions() {
 
 #### Pseudo-code for successfully executing VMXON
 
+p.4233
+
 ```
 IF (register operand) or (CR0.PE = 0) or (CR4.VMXE = 0) or (RFLAGS.VM = 1) or (IA32_EFER.LMA = 1 and CS.L = 0)
 THEN #UD;
@@ -285,3 +289,4 @@ FI;
 [^3]: [0xax](https://0xax.gitbooks.io/linux-insides/content/Theory/linux-theory-3.html)
 [^4]: [Intel SDM 2024 Vol. 3](https://cdrdv2.intel.com/v1/dl/getContent/671447)
 [^5]: [CPU Registers x86](https://wiki.osdev.org/CPU_Registers_x86)
+[⁶]: [The basics of Intel VT-x extensions](https://research.meekolab.com/the-basics-of-intel-vt-x-extensions#heading-vmxon-execution)