They have published multiple major TTS papers since the original WaveNet paper in 2016. Including the recent Tacotron results with impressive style control.

Tacotron (Mar. 2017): https://arxiv.org/abs/1703.10135

Parallel WaveNet (Nov. 2017): https://arxiv.org/abs/1711.10433

Tacotron again (Mar 2018): https://arxiv.org/abs/1803.09017

Tacotron 2 audio samples: https://google.github.io/tacotron/publications/global_style_...