The first statement for the observers solved the problem with the sidebox.
This is the modified statement in case some one else needs it:
Code:
$listing_split = new splitPageResults(cat_filter ($listing_sql_new), MAX_DISPLAY_PRODUCTS_LISTING, 'p.products_id', 'page');
The problem with the Books by the same Author in the product description page was solved by adding the cat_filter in the template tpl like this:
Code:
echo cat_filter($authors_related_products_html);
Thank you verry mutch for your help and if you need testing with new versions of your module you can count on me.
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