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# Analytical index

```{note}
The SUM, if more than 40 pages, shall include an index containing a systematic list of topics from the user’s point of view, the major synonyms and variants (especially if these are well known to users but are not employed in the operational manual for technical reasons), pointing to topics in the body of the manual by:

- page number,
- section number,
- illustration number,
- primary index entry (one level of reference only).

> NOTE Index entries usefully contain auxiliary information, especially cross‐references to contrasting or related terms. For example, the entry for INSERT says ’see also DELETE’. Indexes are made particularly helpful if attention is drawn primarily to important keywords, and to important locations in the body of the manual. This is achieved by highlighting such entries, and by grouping minor entries under major headings. Indexes do not contain more than two levels of entry. If a single index points to different kinds of location, such as pages and illustration numbers, these are unambiguously distinguished, (e.g. Page 35, Figure 7), since the use of highlighting (35, 7) is not for instance sufficient to prevent confusion in this case.
```