How to display posts related to a category if the category is set in the field type matrix (Craft CMS)?

Question

Twig

There are posts with data about books. There is an entity "category" with authors. But the authors should not be specified directly in the post, but using the matrix field type, one of the field types of which is the "author" category.

Screenshots

Настройки самого поля:

Размещение в посте:

If the author were specified directly, without matrix, then a simple construction in twig would work to display all the books of the author on the category page:

{% for entry in craft.entries.section('bookPost').relatedTo(category) %}
  {{ entry.title }}
{% endfor %}

But in the case of matrix, this does not work. On the one hand, it is clear why, but it is not clear how to make it work?