Posted on August 31, 2021.

The 1st author suggested to withdraw the paper after the paper got accepted and the conference registration was paid. The 2nd and the 3rd authors agreed to withdraw the paper, and informed the conference organizer. The conference organizer said that he would handle the withdrawal. A few months later, the 2nd author found that the paper was indeed published. The conference organizer explained that the paper was published because the publisher had received the registraiton fee. The 2nd author immeidately consulted the 1st author regarding the situation, but the 1st author did not respond. As a result, the paper remains to be "published". If the 1st author sees this message, he is encoruaged to contact the 2nd author. The 1st author may also contact the publisher to withrdraw the paper.