The first reason is that the paper has not been included in HowNet, because users need to be audited by the staff of the other party to publish the paper. In addition to certain requirements for the repetition rate of the paper, the quality of the paper must also meet the standards of the other party. If the paper is judged to be unqualified after review, the user cannot view the corresponding paper on HowNet; The second reason is that the user entered the wrong title of the paper, which caused the HowNet system to be unable to correctly identify the corresponding paper materials.