I. INTRODUCTION  
II. A TAXONOMY OF E2E MODELS IN ASR  
III. ARCHITECTURE IMPROVEMENTS TO BASIC E2E MODELS  
IV. TRAINING E2E MODELS  
V. DECODING E2E MODELS  
VI. LM INTEGRATION  
VII. RELATIONSHIP TO CLASSICAL ASR  
VIII. OVERALL PERFORMANCE TRENDS OF E2E APPROACHES IN COMMON BENCHMARKS  
IX. DEPLOYMENT OF E2E MODELS  
X. AREAS FOR FUTURE WORK  
XI. CONCLUSIONS