Here's a chance to hear the full version of Just A Notion, of which only a small re-edited snippet was released in the ABBA Undeleted medley. It's not sung by ABBA; rather, it's sung by ABBA tribute group Arrival.
While the vocals can certainly not be compared to those of Agnetha and Frida's, the real reason for listening to this recording is essentially to get a feel for how the full ABBA version would have sounded.
Also, Björn Again's live version of Just Like That, with an excellent synthesiser melody in place of ABBA's nothingness/nananas/saxophone, is possibly the best-produced ABBA tribute song ever. It captures the energy and emotion that Björn and Benny were originally, and - at least in their opinions - unsuccessfully, looking for when recording Just Like That with ABBA.