From the Cambridge Uni website:
//'Under Article 50, as set out in the Lisbon Treaty, the UK would remain an EU member state for two years while negotiations take place. There is a possibility for the timescale for negotiations to be extended, says Armstrong, but any EU state could veto any extension forcing the UK into a take-it or leave-it dilemma as the clock runs down.
Vote Leave argue that Brexit could utilise alternative legal procedures to extricate the UK from the EU, citing the example of Greenland’s EU withdrawal, or using the Vienna Convention of international treaty law.//
Strange times ahead.