Question: What are multilingual models that were outperformed in performed experiment?
Answer: Direct source$\rightarrow $target: A standard NMT model trained on given source$\rightarrow $target, Multilingual: A single, shared NMT model for multiple translation directions, Many-to-many: Trained for all possible directions among source, target, and pivot languages, Many-to-one: Trained for only the directions to target language