better integrated with updated scripts chapter

Author: shannona

docs/09_1_Sending_a_Transaction_with_a_Locktime.md

@@ -34,20 +34,20 @@ and it's available through `bitcoin-cli` (which is why it's the only
 timelock covered in this section). A parallel method, which locks a
 transaction with a relative time, is defined in [BIP
 68](https://github.com/bitcoin/bips/blob/master/bip-0068.mediawiki)
-and covered in [§11.3: Using CSV in
-Scripts](11_3_Using_CSV_in_Scripts.md).
+and covered in [§13.3: Using CSV in
+Scripts](13_3_Using_CSV_in_Scripts.md).
 
-> Bitcoin Script further empowers both sorts of timelocks, allowing
-for the locking of individual outputs instead of entire
-transactions. Absolute timelocks do so with the Script opcode
+> Bitcoin Script and its "opcodes" further empowers both sorts of
+timelocks, allowing for the locking of individual outputs instead of
+entire transactions. Absolute timelocks do so with the Script opcode
 OP_CHECKLOCKTIMEVERIFY, which is defined in [BIP
 65](https://github.com/bitcoin/bips/blob/master/bip-0065.mediawiki)
-and covered in [§11.2: Using CLTV in
-Scripts](11_2_Using_CLTV_in_Scripts.md), while relative timelocks aare
+and covered in [§13.2: Using CLTV in
+Scripts](13_2_Using_CLTV_in_Scripts.md), while relative timelocks aare
 linked to the Script opcode OP_CHECKSEQUENCEVERIFY, which is defined
 in [BIP
 112](https://github.com/bitcoin/bips/blob/master/bip-0112.mediawiki)
-and also covered in [§11.3](11_3_Using_CSV_in_Scripts.md).
+and also covered in [§13.3](13_3_Using_CSV_in_Scripts.md).
 
 ## Create a Locktime Transaction
 

docs/09_2_Sending_a_Transaction_with_Data.md

@@ -3,7 +3,9 @@
 The final way to vary how you send a basic transaction is to use the
 transaction to send data instead of funds (or really, in addition to
 funds). This gives you the ability to embed information in the
-blockchain. It is done through a special `OP_RETURN` command.
+blockchain. It is done through a special `OP_RETURN` command, which is
+another opcode, an element of Bitcoin scripts that we'll meet in
+[§11.1](11_1_Understanding_the_Foundation_of_Transactions).
 
 The catch? It's controversial. Many people think you shouldn't put
 data onto the Bitcoin chain at all. For a long time, `OP_RETURN` was