Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.

The company had an IPO on the NASDAQ in 1996 and in 1997 Europe's largest telecommunications company, Deutsche Telekom, bought a 21.1 percent stake in VocalTec for $48.3 million, in addition to purchasing $30 million in telephony products, services, and support over the following two-and-a-half years.
What stock exchange is VocalTec associated with?