3GPP 21.900 v20.0.0 — the document's own text
4.9 "Withdrawing" of specifications
Taught in 3. What a Release is, and what freezing one costs (How standards actually get made, in depth), 4. The change request and the release (How standards actually get made, overview).
A TSG may decide to withdraw a specification which is obsolete if its remaining available would confuse implementors (for example, if it contained provisions which were contradictory to provisions of other, later, specifications).
Before withdrawing a specification, the TSG shall ensure that no references are made to it from any other 3GPP specification (and raise appropriate Change Requests to eliminate any such references discovered).
A TSG shall use the procedure in clause 4.9B to withdraw specifications and functionality.