README.md in alipay-0.3.1 vs README.md in alipay-0.4.0

@@ -43,12 +43,12 @@
 
 ### Generate payment url for web
 
 ```ruby
 options = {
-  :out_trade_no      => 'YOUR_ORDER_ID',         # 20130801000001
-  :subject           => 'YOUR_ORDER_SUBJECCT',   # Writings.io Base Account x 12
+  :out_trade_no      => 'YOUR_ORDER_ID',
+  :subject           => 'YOUR_ORDER_SUBJECCT',
   :logistics_type    => 'DIRECT',
   :logistics_fee     => '0',
   :logistics_payment => 'SELLER_PAY',
   :price             => '10.00',
   :quantity          => 12,
@@ -124,9 +124,21 @@
 <?xml version="1.0" encoding="utf-8"?>
 <alipay>
   <is_success>F</is_success>
   <error>TRADE_STATUS_NOT_AVAILD</error>
 </alipay>
+```
+
+## Single trade query
+
+The parameters same as [Close trade](#user-content-close-trade)
+
+```ruby
+Alipay::Service.single_trade_query(
+  :trade_no     => 'TRADE_NO',
+  :out_order_no => 'the-out-order-no'
+)
+# => '<?xml version="1.0" encoding="utf-8"?><alipay><is_success>T</is_success><request><param name="trade_no">TRADE_NO</param><param name="_input_charset">utf-8</param><param name="service">single_trade_query</param><param name="partner">PARTNER</param></request><response><trade><additional_trade_status>DAEMON_CONFIRM_CLOSE</additional_trade_status><buyer_email>[e-mail]</buyer_email><buyer_id>BUYER_ID</buyer_id><discount>0.00</discount><flag_trade_locked>0</flag_trade_locked><gmt_close>2015-01-20 02:37:00</gmt_close><gmt_create>2015-01-20 02:17:00</gmt_create><gmt_last_modified_time>2015-01-20 02:37:00</gmt_last_modified_time><is_total_fee_adjust>F</is_total_fee_adjust><operator_role>B</operator_role><out_trade_no>OUT_TRADE_NO</out_trade_no><payment_type>1</payment_type><price>640.00</price><quantity>1</quantity><seller_email>[e-mail]</seller_email><seller_id>SELLER_ID</seller_id><subject>YOUR ORDER SUBJECT</subject><to_buyer_fee>0.00</to_buyer_fee><to_seller_fee>0.00</to_seller_fee><total_fee>640.00</total_fee><trade_no>TRADE_NO</trade_no><trade_status>TRADE_CLOSED</trade_status><use_coupon>F</use_coupon></trade></response><sign>SIGN</sign><sign_type>MD5</sign_type></alipay>'
 ```
 
 ### Refund
 
 ```ruby