Seminal Papers in ASR
This list is ever-growing… if you have a paper to add, let me know:)
i-vectors
Dehak et al. (2010) Front-End Factor Analysis For Speaker Verification
Seminal i-vector paper. The application is speaker identification.
Soan et al. (2013) Speaker Adaptation of Neural Network Acoustic Models Using I-Vectors
First use of i-vectors for DNN speaker adaptation in ASR.

Context-Dependent Triphone State-Tying
Young et al. (1994) Tree-based state tying for high accuracy acoustic modelling
Weighted Finite-State Transducer Decoding
Mohri et al. (2001) Weighted Finite-State Transducers in Speech Recognition
MLLR Adaptation
Leggetter & Woodland (1995) Maximum likelihood linear regression for speaker adaptation of continuous density hidden Markov models