This is the Act that caused the Referendum which will result in Article 50 being triggered. The Act is notable for completely failing to specify what would happen if the UK voted to leave the EU.  These omissions allowed the Supreme Court to require the UK Government to get Parliamentary authority before triggering Article 50.

Section 1 The Referendum

(1) A referendum is to be held on whether the United Kingdom should remain a member of the European Union.
(2) The Secretary of State must, by regulations, appoint the day on which the referendum is to be held.
(3) The day appointed …