But the CRF, effective when handling sequence labelling tasks such as NER, is not suitable for predicting mentions, as mentions can be nested.
as a rule of thumb, of the two best-known forms of crowdsourcing, microtask crowdsourcing us-ing platforms such as amazon Mechanical Turk is best to label small to medium size amounts of data in a short time, and for labelling data of no intrinsic interest.