Identify additional retracted articles

[wgmueller1]

Currently we have 384 retraction notices:
Paths of the XML files:
https://github.com/AI-ON/biomedical-retractions/blob/master/data/retractions/retractions.csv
Parsed information:
https://github.com/AI-ON/biomedical-retractions/blob/master/retract_features/retract_info_all.txt

These retraction notices cite the original articles in the XML. Parsing the citations gave us 258 original articles:

https://github.com/AI-ON/biomedical-retractions/blob/master/data/retractions/retractions_original_articles.csv

We need to identify additional retracted articles.