1 Introduction

2 Multiway NMT  
2.1 Prototypical Approaches  
2.2 Controlling Parameter Sharing  
2.3 Training Protocols  

3 Low or Zero-Resource MNMT  
3.1 Transfer Learning  
3.2 Pivoting  
3.3 Zero-Shot  

4 Multi-Source NMT  

5 Multilingualism in Older Paradigms  

6 Datasets and Resources  

7 Connections with Domain Adaptation  

8 Future Research Directions  

9 Conclusion