When making the prediction for token instance x i , we record the label assignment distribution for all token instances for the same token type in the previous 1000 words.
if the token instance is "Australia", and in the previous 1000 tokens, the token type "Australia" was twice assigned the label L-ORG and three times the label U-LOC, then the prediction history feature will be: (L − ORG : 2 5 ; U − LOC : 3 5 ).