Journal Article 3 Long short-term memory (LSTM) Concentration 1 Convolutional neural networks (CNN) 1 Deep neural network 1 E-learner 1 E-learning 1 mehr ... Gated recurrent units(GRU) 1 Grid search 1 Non-manufacturing purchasing managers’ index 1 Principal component analysis 1 Purchasing managers’ index 1 Recurrent neural networks (RNN) 1 Sentiment analysis 1 Text mining 1 Time series 1 weniger ...