ROC vs stability in z domain? I have read in some dsp texts that when ROC includes unit circle,system is stable 

But i am bit confused in difference between stability and marginal stability depending Upon ROC

Especially i am confused by part c of below dsp.se question 

Z transform stability

Where in part C, ROC is 1/3 &lt; |z| &lt; 1 and analysis answer of part c is written as "non-causal &amp; marginally stable" . I am confused by marginal stability. why it is marginally stable?If our ROC is changed to 1/3 &lt; |z| &lt; 1.1, will now it becomes stable or will it still remains marginally stable?
Marginally stable means that an otherwise stable system has one or more simple poles on the unit circle (in discrete time), or on the imaginary axis (in continuous time).

The consequence of that is that transients don't decay, but they also don't grow without bounds. Marginally stable systems are unstable in the bounded-input bounded-output (BIBO) sense.