Please, take a look at section, 1.2.3 (Signal Duration), Page-03, of the book Shaum's Outlines: Digital Signal Processing by by Monson H. Hayes.
But, I cannot visualize a two-sided signal.
What would an two sided signal look like?
All I need is to see a double-sided signal. As far as I know, a double sided signal is a complex exponential signal. So, that means it should be a plot of a complex exponential function. Am I correct?