Other articles in the article group contain an article index but not this article.
Explanation:
The Article Index allows you to determine the position of the article within the article group. It is a way of sorting the articles within the article group using Excel. When a position has been filled in, a position must be entered for all the associated group articles so that the entire group can be sorted correctly.
Solution:
In order to be able to determine the correct order of all articles within one article group, the corresponding article indexes must form an ascending sequence of numbers. Therefore, within one article group, each article index must be unique.
