Had to produce the rules to attempt to convert LORLS rather lax material descriptions into SUs of the appropriate type (book, book chapter, journal, journal article, electronic resource or note). This decision is currently made using a variety of hints. For example book chapters are distinguished from journal article by the lack of an issue number and if the partauthor field isn’t filled in, or if the control number looks like an ISSN rather than an ISBN. It probably isn’t perfect but hopefully it will get 90% of the works right. And as long as most of the rest look OK when rendered, most folk won’t notice anyway!