S1AP层的cause对应的value值在规范哪里可以找到？

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如题，我看pcap包里有个别的value代码，如User Inactivity为20，具体的在哪个规范哪章可以找到，如下：

cause  value	S1AP cause	Meaning
	Unspecified	Sent  for radio network layer cause when none of the specified cause values  applies.
	TX2RELOCOverall  Expiry	The  timer guarding the handover that takes place over X2 has abnormally expired.
	Successful  Handover	Successful  handover.
	Release  due to E-UTRAN generated reason	Release  is initiated due to E-UTRAN generated reason.
	Handover  Cancelled	The  reason for the action is cancellation of Handover.
	Partial  Handover	Provides  a reason for the handover cancellation. The HANDOVER COMMAND message from MME  contained E-RABs to Release List  IE and the source eNB estimated service continuity for the UE would be better  by not proceeding with handover towards this particular target eNB.
	Handover  Failure In Target EPC/eNB Or Target System	The  handover failed due to a failure in target EPC/eNB or target system.
	Handover  Target not allowed	Handover  to the indicated target cell is not allowed for the UE in question.