Added reference link

LSTMtutorial.py

@@ -5,6 +5,8 @@
 
 @author: yjiang
 Reference: http://machinelearningmastery.com/time-series-prediction-lstm-recurrent-neural-networks-python-keras/
+http://machinelearningmastery.com/understanding-stateful-lstm-recurrent-neural-networks-python-keras/
+http://colah.github.io/posts/2015-08-Understanding-LSTMs/
 """
 
 # LSTM for international airline passengers problem with regression framing
@@ -25,6 +27,7 @@ def create_dataset(dataset, look_back=1):
 		dataX.append(a)
 		dataY.append(dataset[i + look_back, 0])
 	return numpy.array(dataX), numpy.array(dataY)
+
 # fix random seed for reproducibility
 numpy.random.seed(7)
 # load the dataset
@@ -40,6 +43,8 @@ def create_dataset(dataset, look_back=1):
 train, test = dataset[0:train_size,:], dataset[train_size:len(dataset),:]
 # reshape into X=t and Y=t+1
 look_back = 1
+
+# why do we need to transform the dataset using look_back
 trainX, trainY = create_dataset(train, look_back)
 testX, testY = create_dataset(test, look_back)
 # reshape input to be [samples, time steps, features]