where is the label if review is positive or negative?

[Sandy4321]

where is the label if the review is positive or negative?
we that they used it for sentiment supervised classification in this paper
https://arxiv.org/abs/1509.01626
Character-level Convolutional Networks for Text Classification
Xiang Zhang, Junbo Zhao, Yann LeCun
and this
https://arxiv.org/abs/1607.01759
Bag of Tricks for Efficient Text Classification
Armand Joulin, Edouard Grave, Piotr Bojanowski, Tomas Mikolov