Effective Preprocessing and Normalization Techniques for COVID-19 Twitter Streams with POS Tagging via Lightweight Hidden Markov Model

Table 1

Openly available social media annotated corpus.

Annotated corpus	Number of tokens	Entity schema
Finin et al. [58]	7 K	Person, location, and organization
Ritter et al. [59]	46 K	Freebase
Liu et al. [3]	12 K	Person, location, product, and organization
Rowe et al. [60]	29 K	Person, location, misc, and organization
Derczynski et al. [61]	165 K	Person, location, and organization