1 Introduction  
2 The Event Extraction Task  
2.1 Definition  
2.2 Corpora  
3 Supervised Learning Models  
3.1 Feature-based Models  
3.2 Neural-based Models  
3.3 Graph Convolutional Neural Networks  
3.4 Knowledge Base  
3.5 Data Generation  
3.6 Document-level Modeling  
3.7 Joint Modeling  
4 Low-resource Event Extraction  
4.1 Zero-shot Learning  
4.2 Few-shot Learning  
4.3 Cross-lingual