diff --git a/README.md b/README.md
index f98329b..2bfaee7 100644
--- a/README.md
+++ b/README.md
@@ -85,6 +85,34 @@ Token parameters are truncated when calculating demurrage and redistribution:
 * Demurrage modifier: 64 bits
 
 
+## Expiration
+
+A token may set to expire at a certain point in time. After the expiry, no more transfers may be executed. From that point on, balances are frozen and demurrage is halted.
+
+Expiration may be set in terms of redistribution periods.
+
+Unless sealed (see below), expiration may be changed at any time to any future redistribution period. However, once expired, expiration may not be changed further.
+
+
+## Supply
+
+Unless sealed (see below), Supply limit may be set and change at any time. Supply may never be directly set to less than the current supply. However, contract _writers_ may burn tokens in their possession using the `burn()` method, which will effectively reduce the supply.
+
+
+## Mutability
+
+The following parameters may not be changed after contract is published:
+
+* Demurrage level
+* Redistribution period
+
+The contract provides a sealing feature which prohibits further changes to parameters that can initially be edited. These include:
+
+* Adding and removing writers (addresses that may mint tokens)
+* Sink addres
+* Expiry period
+* Supply limit
+
 
 ## Gas usage
 
diff --git a/solidity/DemurrageTokenSingleNocap.sol b/solidity/DemurrageTokenSingleNocap.sol
index 975eaad..9b3edbd 100644
--- a/solidity/DemurrageTokenSingleNocap.sol
+++ b/solidity/DemurrageTokenSingleNocap.sol
@@ -121,7 +121,7 @@ contract DemurrageTokenSingleNocap {
 
 	// Implements Sealer
 	uint256 public sealState;
-	uint8 constant MINTER_STATE = 1;
+	uint8 constant WRITER_STATE = 1;
 	uint8 constant SINK_STATE = 2;
 	uint8 constant EXPIRY_STATE = 4;
 	uint8 constant CAP_STATE = 8;
@@ -223,7 +223,7 @@ contract DemurrageTokenSingleNocap {
 
 	// Given address will be allowed to call the mintTo() function
 	function addWriter(address _minter) public returns (bool) {
-		require(!isSealed(MINTER_STATE));
+		require(!isSealed(WRITER_STATE));
 		require(msg.sender == owner);
 		minter[_minter] = true;
 		return true;
@@ -231,7 +231,7 @@ contract DemurrageTokenSingleNocap {
 
 	// Given address will no longer be allowed to call the mintTo() function
 	function deleteWriter(address _minter) public returns (bool) {
-		require(!isSealed(MINTER_STATE));
+		require(!isSealed(WRITER_STATE));
 		require(msg.sender == owner || _minter == msg.sender);
 		minter[_minter] = false;
 		return true;