[1] 8 Parts of Speech:
http://www.butte.edu/departments/cas/tipsheets/grammar/parts_of_speech.html
[2] Parts of Speech overview:
http://partofspeech.org/
[3] spaCy Annotation Specifications:
https://spacy.io/api/annotation#pos-tagging
[4] Hidden Markov Model:
https://en.wikipedia.org/wiki/Hidden_Markov_model
[5] A simple rule-based part of speech tagger:
http://www.aclweb.org/anthology/A92-1021
[6] displaCy:
https://explosion.ai/demos/displacy
[7] ntlk tag module:
https://www.nltk.org/api/nltk.tag.html
[8] nltk chapter 5:
https://www.nltk.org/book/ch05.html
[9] Training NLTK tagger:
http://textminingonline.com/dive-into-nltk-part-iii-part-of-speech-tagging-and-pos-tagger
[10] AI in Practice: Identifying Parts of Speech in Python:
https://medium.com/@brianray_7981/ai-in-practice-identifying-parts-of-speech-in-python-8a690c7a1a08
[11] Speech Tagging in TextBlob...