diff --git a/contracts/UniswapV2Factory.sol b/contracts/UniswapV2Factory.sol
index f06ec1a..0ecf4c1 100644
--- a/contracts/UniswapV2Factory.sol
+++ b/contracts/UniswapV2Factory.sol
@@ -1,73 +1,54 @@
 pragma solidity 0.5.12;
 
 import "./interfaces/IUniswapV2Factory.sol";
-
 import "./UniswapV2.sol";
 
 contract UniswapV2Factory is IUniswapV2Factory {
     bytes public exchangeBytecode;
 
-    mapping (address => address[2]) private exchangeToTokens;
-    mapping (address => mapping(address => address)) private token0ToToken1ToExchange;
-    mapping (address => address[]) private tokensToOtherTokens;
-    address[] public exchanges;
+    mapping (address => mapping(address => address)) private _getExchange;
+    mapping (address => address[2]) private _getTokens;
+    address[] public getExchanges;
 
     event ExchangeCreated(address indexed token0, address indexed token1, address exchange, uint exchangeNumber);
 
     constructor(bytes memory _exchangeBytecode) public {
-        require(_exchangeBytecode.length >= 0x20, "UniswapV2Factory: SHORT_BYTECODE");
+        require(_exchangeBytecode.length >= 32, "UniswapV2Factory: SHORT_BYTECODE");
         exchangeBytecode = _exchangeBytecode;
     }
 
-    function getTokens(address exchange) external view returns (address token0, address token1) {
-        return (exchangeToTokens[exchange][0], exchangeToTokens[exchange][1]);
-    }
-
-    function getExchange(address tokenA, address tokenB) external view returns (address exchange) {
-        (address token0, address token1) = getTokenOrder(tokenA, tokenB);
-        return token0ToToken1ToExchange[token0][token1];
-    }
-
-    function getOtherTokens(address token) external view returns (address[] memory) {
-        return tokensToOtherTokens[token];
-    }
-
-    function getOtherTokensLength(address token) external view returns (uint) {
-        return tokensToOtherTokens[token].length;
-    }
-
-    function getExchangesLength() external view returns(uint) {
-        return exchanges.length;
-    }
-
-    function getTokenOrder(address tokenA, address tokenB) private pure returns (address token0, address token1) {
+    function sortTokens(address tokenA, address tokenB) public pure returns (address, address) {
         return tokenA < tokenB ? (tokenA, tokenB) : (tokenB, tokenA);
     }
 
+    function getExchange(address tokenA, address tokenB) external view returns (address) {
+        (address token0, address token1) = sortTokens(tokenA, tokenB);
+        return _getExchange[token0][token1];
+    }
+
+    function getTokens(address exchange) external view returns (address, address) {
+        return (_getTokens[exchange][0], _getTokens[exchange][1]);
+    }
+
+    function getExchangesCount() external view returns (uint) {
+        return getExchanges.length;
+    }
+
     function createExchange(address tokenA, address tokenB) external returns (address exchange) {
         require(tokenA != tokenB, "UniswapV2Factory: SAME_ADDRESS");
         require(tokenA != address(0) && tokenB != address(0), "UniswapV2Factory: ZERO_ADDRESS");
-
-        (address token0, address token1) = getTokenOrder(tokenA, tokenB);
-        require(token0ToToken1ToExchange[token0][token0] == address(0), "UniswapV2Factory: EXCHANGE_EXISTS");
+        (address token0, address token1) = sortTokens(tokenA, tokenB);
+        require(_getExchange[token0][token1] == address(0), "UniswapV2Factory: EXCHANGE_EXISTS");
 
         bytes memory exchangeBytecodeMemory = exchangeBytecode;
         bytes32 salt = keccak256(abi.encodePacked(token0, token1));
-        assembly {
-            exchange := create2(
-                0,
-                add(exchangeBytecodeMemory, 0x20),
-                mload(exchangeBytecodeMemory),
-                salt
-            )
+        assembly { // solium-disable-line security/no-inline-assembly
+            exchange := create2(0, add(exchangeBytecodeMemory, 32), mload(exchangeBytecodeMemory), salt)
         }
         UniswapV2(exchange).initialize(token0, token1);
 
-        exchangeToTokens[exchange] = [token0, token1];
-        token0ToToken1ToExchange[token0][token1] = exchange;
-        tokensToOtherTokens[token0].push(token1);
-        tokensToOtherTokens[token1].push(token0);
-
-        emit ExchangeCreated(token0, token1, exchange, exchanges.push(exchange));
+        _getExchange[token0][token1] = exchange;
+        _getTokens[exchange] = [token0, token1];
+        emit ExchangeCreated(token0, token1, exchange, getExchanges.push(exchange));
     }
 }
diff --git a/contracts/interfaces/IERC20.sol b/contracts/interfaces/IERC20.sol
index c8fe754..17b2f29 100644
--- a/contracts/interfaces/IERC20.sol
+++ b/contracts/interfaces/IERC20.sol
@@ -11,6 +11,10 @@ interface IERC20 {
     function balanceOf(address owner) external view returns (uint);
     function allowance(address owner, address spender) external view returns (uint);
 
+    function DOMAIN_SEPARATOR() external view returns (bytes32);
+    function APPROVE_TYPEHASH() external pure returns (bytes32);
+    function nonces(address owner) external view returns (uint);
+
     function transfer(address to, uint value) external returns (bool);
     function approve(address spender, uint value) external returns (bool);
     function transferFrom(address from, address to, uint value) external returns (bool);
@@ -18,9 +22,6 @@ interface IERC20 {
     function burn(uint value) external;
     function burnFrom(address from, uint value) external;
 
-    function DOMAIN_SEPARATOR() external view returns (bytes32);
-    function APPROVE_TYPEHASH() external pure returns (bytes32);
-    function nonces(address owner) external view returns (uint);
 
     function approveMeta(
         address owner, address spender, uint value, uint nonce, uint expiration, uint8 v, bytes32 r, bytes32 s
diff --git a/contracts/interfaces/IUniswapV2Factory.sol b/contracts/interfaces/IUniswapV2Factory.sol
index ed85de8..c901c36 100644
--- a/contracts/interfaces/IUniswapV2Factory.sol
+++ b/contracts/interfaces/IUniswapV2Factory.sol
@@ -4,13 +4,12 @@ interface IUniswapV2Factory {
     event ExchangeCreated(address indexed token0, address indexed token1, address exchange, uint256 exchangeNumber);
 
     function exchangeBytecode() external view returns (bytes memory);
-    function exchanges(uint256) external view returns (address);
 
-    function getTokens(address exchange) external view returns (address, address);
+    function sortTokens(address tokenA, address tokenB) external pure returns (address, address);
     function getExchange(address tokenA, address tokenB) external view returns (address);
-    function getOtherTokens(address token) external view returns (address[] memory);
-    function getOtherTokensLength(address token) external view returns (uint256);
+    function getTokens(address exchange) external view returns (address, address);
+    function getExchanges() external view returns (address[] memory);
+    function getExchangesCount() external view returns (uint);
 
     function createExchange(address tokenA, address tokenB) external returns (address exchange);
-    function getExchangesLength() external view returns(uint256);
 }
diff --git a/contracts/token/ERC20.sol b/contracts/token/ERC20.sol
index 4e16a22..10bfd00 100644
--- a/contracts/token/ERC20.sol
+++ b/contracts/token/ERC20.sol
@@ -7,15 +7,13 @@ import "../libraries/SafeMath.sol";
 contract ERC20 is IERC20 {
     using SafeMath for uint;
 
-    // ERC-20 data
     string public name;
     string public symbol;
     uint8 public decimals;
-    uint public totalSupply;
+    uint  public totalSupply;
     mapping (address => uint) public balanceOf;
     mapping (address => mapping (address => uint)) public allowance;
 
-    // ERC-721 data
 	bytes32 public DOMAIN_SEPARATOR;
     // keccak256("Approve(address owner,address spender,uint256 value,uint256 nonce,uint256 expiration)");
 	bytes32 public constant APPROVE_TYPEHASH = hex'25a0822e8c2ed7ff64a57c55df37ff176282195b9e0c9bb770ed24a300c89762';
@@ -85,6 +83,7 @@ contract ERC20 is IERC20 {
         external
     {
         require(nonce == nonces[owner]++, "ERC20: INVALID_NONCE");
+        // solium-disable-next-line security/no-block-members
         require(expiration > block.timestamp, "ERC20: EXPIRED_SIGNATURE");
         require(v == 27 || v == 28, "ECDSA: INVALID_V");
         require(uint(s) <= 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0, "ECDSA: INVALID_S");
diff --git a/contracts/token/SafeTransfer.sol b/contracts/token/SafeTransfer.sol
index f29af94..4310b56 100644
--- a/contracts/token/SafeTransfer.sol
+++ b/contracts/token/SafeTransfer.sol
@@ -2,14 +2,11 @@ pragma solidity 0.5.12;
 
 contract SafeTransfer {
     function safeTransfer(address token, address to, uint value) internal {
+        // solium-disable-next-line security/no-low-level-calls
         (bool success, bytes memory data) = token.call(abi.encodeWithSignature("transfer(address,uint256)", to, value));
-
-        require(success, "SafeTransfer: SWAP_REVERTED");
-
-        if (data.length == 32) {
+        require(success, "SafeTransfer: SWAP_FAILED");
+        if (data.length > 0) {
             require(abi.decode(data, (bool)), "SafeTransfer: SWAP_UNSUCCESSFUL");
-        } else if (data.length > 32) {
-            revert("SafeTransfer: SWAP_INVALID_RETURN");
         }
     }
 }
\ No newline at end of file