0. Abstract
1. Introduction
Goal
Contribution
2. Definition of cross-lingual learning
2.1 Definition
2.2 Terminology note
3. Methodology
3.1 Selection
3.2 Observed aspects
3.3 Limitations
4. Tasks, datasets and languages
5. Cross-lingual resources and technologies
5.1 Multilingual distributional representations
5.2 Parallel corpus
5.3 Word alignments
5.4 Machine translation
5.5 Universal features
5.6 Bilingual dictionary
5.7 Pre-trained multilingual language models
5.8 Language features
5.9 Others
6. Transfer paradigms
6.1 Label transfer
6.1.1 Correspondence
6.1.2 Projection
6.1.3 Zero-shot and multi-source learning
6.1.4 Reducing noise
6.2 Feature transfer
6.3 Parameter transfer
6.3.1 Language independent representations
6.3.2 Joint learning techniques
6.3.3 Cascade learning techniques
6.3.4 Layer-specific strategies
6.3.5 Multi-source learning
6.3.6 Pre-trained multilingual language models
6.4 Representation transfer
6.5 Comparison and summary
7. Feature directions
7.1 Multilingual datasets
7.2 Stadardization of linguistic resources
7.3 Pre-trained multilingual language models
7.4 Truly low-resource languages and excluded languages
7.5 Parameter sharing strategy search
7.6 Curse of multilinguality
7.7 Combination with multitask learning
7.8 Word alignments
7.9 Machine translation
8. Conclusions