NLP Addition: Clinical NLP Challenges

[tnaumann]

Add Clinical NLP Challenges Datasets from Filannino and Uzuner's Advancing the State of the Art in Clinical Natural Language Processing through Shared Tasks. While some are already included (e.g. TREC), others could be added (e.g. CLEF/eHealth). May requires a followup checklist to track since there are a number indicated in Table 1.