I've been looking through the Broadside magazine archives and I was very happy to find they have music for Keep On Keepin' On by Len Chandler, but I'm confused by one things. D7/3* appears with the chords with * stating (3rd on bass). Can anyone let me know what this means? I'm sure it's something incredibly simple, but it's got me stumped. Here's the link to the music, it's on page 3.

http://www.broadsidemagazine.com/All/34.pdf