diff --git a/blockchain/README.md b/blockchain/README.md
index 60ea87b..0cc75d5 100644
--- a/blockchain/README.md
+++ b/blockchain/README.md
@@ -7,8 +7,8 @@
 
 ## What we measurement?
 
-- Count step/effort to complete suspend all relevant fund/transaction.
-- TBD
+- Meantime to response. After the alert system triggers, how much time to freeze the fund that is relative to the fraudulent.
+- Meantime to resolve. After the alert system triggers, how much time to freeze the fund that is relative to the fraudulent and funds are retrieved.
   
 <!-- Response Time, Recovery Time and Post-Incident Analysis -->
 
diff --git a/contracts/libraries/Forest.sol b/contracts/libraries/Forest.sol
index 9e8dc19..1171eb8 100644
--- a/contracts/libraries/Forest.sol
+++ b/contracts/libraries/Forest.sol
@@ -7,8 +7,6 @@ pragma solidity >=0.8.0 <0.9.0;
  * @author Sirawit Techavanitch (sirawit_tec@live4.utcc.ac.th)
  */
 
-// @TODO merging Tx (allowing only same root).
-
 library Forest {
     /**
      * @dev Structure representing a transaction.
@@ -139,4 +137,11 @@ library Forest {
 
         emit TransactionSpent(id, value);
     }
+
+    /**
+     * @notice not suitable for use in production.
+     */
+    function mergeTx(DAG storage self, bytes32 [] memory ids) internal {
+        // @TODO
+    }
 }
diff --git a/contracts/libraries/UTXO.sol b/contracts/libraries/UTXO.sol
index a930c80..c860589 100644
--- a/contracts/libraries/UTXO.sol
+++ b/contracts/libraries/UTXO.sol
@@ -4,13 +4,16 @@ pragma solidity >=0.8.0 <0.9.0;
 /**
  * @title Unspent Transaction Output Model (UTXO)
  * @notice This library implements the UTXO model for managing transactions on the blockchain.
+ * inspired from:
+ * https://gist.github.com/alex-miller-0/a5f4de3f811872b7272e66a3697f88de
+ * https://github.com/ProjectWyvern/wyvern-ethereum/blob/master/contracts/token/UTXORedeemableToken.sol
+ * https://github.com/olegfomenko/utxo
  * @author Sirawit Techavanitch (sirawit_tec@live4.utcc.ac.th)
  */
+
 import "@openzeppelin/contracts/utils/cryptography/ECDSA.sol";
 import "@openzeppelin/contracts/utils/cryptography/MessageHashUtils.sol";
 
-// @TODO merging UTXO.
-
 library UnspentTransactionOutput {
     using ECDSA for bytes32;
     using MessageHashUtils for bytes32;
@@ -188,6 +191,15 @@ library UnspentTransactionOutput {
         emit TransactionConsumed(id);
     }
 
+    /**
+     * @notice merge multiple transaction into single transaction.
+     * @param self The UTXO storage.
+     * @param ids The array of the identifiers of the transaction to merge.
+     */
+    function mergeTx(UTXO storage self, bytes32 [] memory ids) internal {
+        // @TODO
+    }
+
     /**
      * @notice Retrieves the details of a transaction from the UTXO.
      * @param self The UTXO storage.