How do you write source cards for a textbook?

Answer 1

A text book is a book, so if the style manual you were instructed to use doesn't have a specific format for "text books", just follow the style for books in general.

If you're talking about elementary or middle school, the author may not be readily apparent. If after a bit of poking around in the "front matter" you can't find an author, treat the publisher as the author (if the problem is that there are fifty or sixty "authors" listed ... list one or two and then say "et al.", which is a Latin abbreviation for "and others").

Answer 2

There should be a primary author for a textbook. If not, you can list the first one or two listed. If none is listed, cite the publisher and year as indicated by the ISBN notice.