Factbox: When and how Italy votes in Sunday's reform referendum

Here are key facts about how the referendum will work and how and when the results will be announced:

-Around 52 million Italians are eligible to vote, of whom just over 4 million are expats living abroad. -Polls will open at 7 a.m. (0600 GMT) and close at 11 p.m.

-The result of exit polls will be announced on Italian television as soon as polls close. These polls will be conducted by five polling agencies commissioned by four TV stations. -State-owned RAI will announce the result of a joint poll by the Piepoli Institute and IPR Marketing, Mediaset will use the Tecne Institute, Sky Italia will use the Quorum agency and La 7 will use EMG Acqua. -The vote count will begin as soon as polls close. After around 30 minutes, the first projections of the result will be announced on the basis of actual votes counted. The projections will be made by the same agencies that do the exit polls.

-The projections will then be updated at regular intervals of around 30 minutes as the count progresses. Each projection should be more accurate than the last. -If the result is not close, the winner is likely to be clear after the second projection, some time between midnight and 1 a.m. (0000 GMT) -If the outcome is extremely close, the winner may not be known until the count is completed, probably between 2:00 and 3:00 am. -The question on the ballot sheet, which has sparked fierce protests from Renzi's opponents who say it does not accurately reflect the contents of the reform and is biased towards 'Yes,' is as follows:

"Do you approve the text of the constitutional law concerning measures to end equal powers for the upper and lower houses of parliament, the reduction of the number of parliamentarians, the containment of costs in running political institutions, the abolition of (public advisory body) Cnel and the amendment of article five of the second part of the Constitution, approved by parliament and published in the official Gazette number 88 on April 15, 2016."

(Reporting by Gavin Jones; Editing by Catherine Evans)