I've been using searches like this for a while:
Code:
author_sort:"~(^[AaBbCcDd])|(&\s*[AaBbCcDd])"
This works perfectly fine, but on multi-author books it matches all authors that begin with the respective letters. Is there a way to search only for the the first "author_sort" entry? The only idea I can come up with is to create a custom field and use the "list_item" template function to fill it, but I'd prefer to use a search instead if possible.