They're worth whatever price shareholders meeting at McDonald's can agree on. Search Craigslist for buyers-sellers. If there are zero buy offers, they are worthless.
'...So what your saying is BioAmber never filed through the courts to cancel the shares to declare them worthless. Guess they ain’t worthless then lol..."
What I'm saying is they filed through the courts for protection from their creditors in order to pursue a restructuring process that ultimately resulted in the liquidation of the company, they were gone at the point where a liquidation was consummated, and that a liquidated company is worthless by definition.
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