Following publication of the article, an undisclosed authorship dispute was claimed by a researcher who were not included in the by-line. It is inappropriate to retract a publication solely on the grounds of such a dispute. However, the institutional investigation where the authors belong concluded that there was an improper mark of authorship, which is beyond the research ethics, by the authors. From this viewpoint, the editor decided to retract the article with this notice. The retraction was agreed by the authors. Of note, there was no reason to doubt the validity of the study findings per se.