Help recovering CD-R session (mac)

[Andre Langevin]

As I lost my hard drive friday, I went back to multiple back-ups I 
had made on CD-R.  One CD-R has a no so funny behaviour.  It has four 
sessions on it, the fourth having "closed" the CD but I can only see 
the last session I put on it.  Is there a way to get the data from 
the previous sessions?  I tried to have access to them through a few 
readers around here including the original burner but with no success.

Thanks for any help.
Andre