By the same reasons, the Category search too is not systematically complete. As with the keywords, it is worthwhile also here to familiarize yourself with the various options. To view them, click on the arrow at the right of the pull-down window. The selection of a particular category can help to reduce the number of titles listed for your "Author, Bible Passage, or Keyword" searches. You may, for example, be interested only in text criticism or literary criticism or topography. Or you may search only for publications on Deuteronomistic literature. Or you want to restrict the findings on literature about the relations between Deuteronomy and the Holiness Code. So indicate just your category. Then the number of the search results will be perceptibly lower but they will be much more specific.
Often, the value of the "Category" search" is not to contribute to the finding of a certain title, but rather to help organize the titles already found. In this way, it helps when you begin to analyze the search results.